how many async-modules can js-app practically load?

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Re: how many async-modules can js-app practically load?

guest271314
> it doesn't actually ```import``` 1000+ es-modules inside the rollup-file. it just creates one es-module that exports a dictionary -- and assigns the dictionary 1000+ vanilla json-objects and functions.

The code provides a means to fetch N resources and export those resources within a single object.

> currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
> in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.
>
> if we're actually committed to native es-modules, then we either
> 1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
> 2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

You still have not clearly defined what you mean by "rolled-up". That language appears to be a random nickname, not any immutable principle that individuals are bound to recognize or observe (even if "rolled-up" were some form of a coding style or standard).

Nor is it clear what you mean by "production". 

There is no external central committee that stamps code as "production". Even if there were no individual is obliged to submit to such a procedure nor have any concern for such an arbitrary and irrelevant presumptive review of code. 

The only observable points are input and output. In general, how output is achieved is immaterial. If there are specific restrictions as to how the output can be achieved then those restrictions need to be clearly defined. 



The original post asked "how many async-modules can js-app practically load?" and mentioned "circular-references" (the thread appears to mainly be about one or more coding styles, not code itself) though as yet no code has been posted which demonstrates "circular-references" or any other coding problem.

On Sun, Jun 2, 2019 at 1:30 AM kai zhu <[hidden email]> wrote:
i played around with your code in jsfiddle [1], and understand it a little more.
it doesn't actually ```import``` 1000+ es-modules inside the rollup-file.
it just creates one es-module that exports a dictionary
 -- and assigns the dictionary 1000+ vanilla json-objects and functions.

```js
// the "rollup-file" is a single es-module
// that exports 1000+ vanilla dictionary-entries
const modules = {};

// this is not a es-module, nor is it rolled-up (external fetch)
modules.image = <await fetch json from gist.github.com>

// this is not a [rolled-up] es-module
modules.fn = function () {...}

// these are not [rolled-up] es-modules
Object.assign(modules, <1000 json-entries>)

export {modules}
```

currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.

if we're actually committed to native es-modules, then we either
1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

```js
// rollup.js with [hypothetical] # delimited es-modules
# module aa
import {bb} as bb;
export ...;

# module bb
export ...;
```

i'm generally skeptical of option 1, given how poorly npmjs.com has handled similar problems deduplicating children in node_modules/ directory.

[1] jsfiddle pseudo-module rollup

On Sat, Jun 1, 2019 at 5:30 PM guest271314 <[hidden email]> wrote:
> your rollup solution is interesting, 

What  is "rollup" referring to? 

> but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  

The duplicate ("collision") entry an ```try..catch``` block is included in the code to demonstrate given an array of module names to be exported and imported as identifiers 1) duplicate entries can be filtered; 2) if a plain object is exported duplicate identifiers ("collision") is not possible as a JavaScript plain object does not have duplicate property names ("collision"); if there is an issue with identifiers in a module the cause would not be the number of async-modules loaded ("how many"), but the naming of the identifiers within the code, using or not using ```const``` or ```let```. Still not sure what the actual issue is?

> don't completely understand how it works, 

Use an ```async``` function to fetch data, check for the described "collision" , create a ```data URI``` to be imported, optionally, append addition code to be executed within the ```<script type="module">```.

> but not sure of suitability for production-use, because of its dynamic <script> tag generation.

What is the issue with dynamic ```<script>``` tag generation? 

There is more than one possible approach to achieve the presumptive requirement, that is still not clear to the exclusion of what is not the expected result.

There were no restrictions described at the OP and following messages other than other than 

pure-es6 application with 20 es-modules rolled-up into one [production] bundle?

The example code uses only JavaScript implementation shipped with the browser without any external, third-party libraries.
 
What standard or definition are you relying for the meaning of the term "production-use"? What procedure are you using to determine if code is "production-use" "suitable"? How is that procedure related to "how many async-modules can js-app practically load?"?



On Sat, Jun 1, 2019 at 9:42 PM kai zhu <[hidden email]> wrote:
your rollup solution is interesting, but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  don't completely understand how it works, but not sure of suitability for production-use, because of its dynamic <script> tag generation.

```console
ReferenceError: module names ["yeqjqb02mvg3yze26rc5"] are not unique
    at data:application/javascript,%0A%20%20%20%20%20%20const%20modules...
```

On Sat, Jun 1, 2019 at 2:33 PM guest271314 <[hidden email]> wrote:
Re: how many async-modules can js-app practically load?

An example of exporting and importing loading 1000 properties in a single module, where duplicate property names are checked for. Since JavaScript plain objects cannot have duplicate property names there should not be any "collisions"; the code can check for and modify the object to be exported, though the last duplicate property name will be exported without any errors thrown unless the code is composed to throw such an error.

```
  (async() => {
    const oneThousandModules = encodeURIComponent(
      // substitute rand for a Set of module names to be exported
      // e.g. const moduleNames = ['moduleA', 'moduleB', ...moduleZ]
      `
      const modules = {};
      // set a function to be exported
      modules.fn = function() {return 'a function'};
      // function to set (1000) 'random' module names to be exported
      const rand = (seed = 'abcdefghijklmnopqrstuvwxyz0123456789', n = 5, len = seed.length) =>
        '.'.repeat(n).replace(/./g, _ => seed[~~(Math.random() * len)]);
        // use Set for unique module identifiers
        const moduleNames = [...Array(1000)].map(_ => rand());
        const moduleIdentifiers = new Set(moduleNames);
        // below line will cause ReferenceError to be thrown
        moduleNames.push(moduleNames[0]);
        try {
          if (moduleIdentifiers.size !== moduleNames.length) {
            // check for duplicates
            const duplicates = moduleNames.filter((moduleName, index) => moduleNames.indexOf(moduleName) !== index);
            // notification of duplicate module names
            throw new ReferenceError('module names ' + JSON.stringify(duplicates) + ' are not unique');
            // perform the designated task if duplicate module names are found here
          }
        } catch (e) {
          console.error(e);
          console.trace();
        }
        // get, set (sync or async) exported module here
        Object.assign(modules, ...[...moduleIdentifiers].map((id, value) => ({[id]:value})));
        // since JavaScript plain object cannot have duplicate property names
        // modules object will still be exported without duplicate property names
        // without collisions
        export {modules}
    `);
    const scriptText = `import {modules} from "data:application/javascript,${oneThousandModules};${encodeURIComponent('console.log(modules);for (const key in modules) {if (typeof modules[key] === \'function\') {console.log(modules[key]());}}')}"`;
    const script = document.createElement("script");
    script.type = "module";
    script.textContent = scriptText;
    document.head.appendChild(script);
  })();
```


On Sat, Jun 1, 2019 at 1:51 AM kai zhu <[hidden email]> wrote:
> Place all of the code to be exported in 1 file?  
 
that obviously will not work, because of module-scope collision.  can anyone share their experience on deploying a [babel-free] pure-es6 application with 20 es-modules rolled-up into one [production] bundle?  is it even possible?


On Fri, May 31, 2019 at 7:55 PM guest271314 <[hidden email]> wrote:
how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?

Place all of the code to be exported in 1 file? 

with some of them having circular-references

Not certain how that is possible when using ```import``` within ```<script type="module">```?

how many async-modules can js-app practically load?

Again, how many have you tried to load? 100? 500? 1000? Either should be possible.

What specific issue are you actually to resolve?

On Fri, May 31, 2019 at 5:40 PM kai zhu <[hidden email]> wrote:
> Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

was that with some combination of babel/rollup/webpack or pure-es6?
if i want to develop a pure-es6 webapp (no babel), how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?


On Fri, May 31, 2019 at 10:47 AM Isiah Meadows <[hidden email]> wrote:
If it's bundled by Rollup or Webpack into a single bundle, it's
equivalent to a single `<script type="module" src="...">` pointing
towards the original entry point, excluding network requests.* But in
either case, you aren't listing 50 scripts, you're only listing the
entry module and importing child modules within parent modules. Rollup
and Webpack do mostly the same thing browsers do when it comes to
resolving dependencies, just they generate a bundle afterwards where
browsers execute code afterwards. Also, it's worth noting that the gap
between a single large request and multiple smaller requests has
shrunk a lot since HTTP/2 came along, since it's binary, it allows
requests and response data to be interleaved, it better leverages the
underlying TCP protocol format, and it allows servers to send data
pre-emptively without the client requesting it first. (Web sockets are
built on this functionality.) It's still better to bundle in general,
but it's less of a problem not to.

This is *not* the case for `<script type="module">` elements - those
operate more like inline scripts that happen to have the ability to
`import`.

Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

* This is, of course, not the case if you are using pure ES6 and you
aren't using any plugins to, say, run the original source through
Babel for React + JSX or something.

-----

Isiah Meadows
[hidden email]
www.isiahmeadows.com
On Sat, May 25, 2019 at 2:12 AM kai zhu <[hidden email]> wrote:
>
> Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
>
> so async-loading 50 ```<script type="module">``` tags
> has equivalent side-effect
> as sync-loading single webpack-rollup (of same 50 modules)?
>
> i have nagging suspicion of doubts.  has anyone tried native async-loading large numbers (>10) of
> ```<script type="module">``` tags, and verify it resolves identically to using a single webpack-rollup?
>
> again, i'm not that knowledgeable on es-modules, so above question may be trivially true, and i'm just not aware.
>
> -kai
>
> On 24 May 2019, at 23:41, Isiah Meadows <[hidden email]> wrote:
>
> There's two main reasons why it scales:
>
> 1. Modules are strongly encapsulated while minimizing global pollution.
> 2. The resolution algorithm applies the same logic no matter how many
> modules are loaded.
>
> It's much easier for it to scale when you write the code unaware of
> how many modules you might be loading and unaware of how deep their
> dependency graph is. Fewer assumptions here is key. It's an
> engineering problem, but a relatively simple one.
>
> If you want a short example of how sync module resolution works, you
> can take a look at this little utility I wrote:
> https://github.com/isiahmeadows/simple-require-loader. That doesn't
> asynchronously resolve modules, but it should help explain the process
> from a synchronous standpoint. Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
> -----
>
> Isiah Meadows
> [hidden email]
> www.isiahmeadows.com
>
> On Thu, May 23, 2019 at 10:49 AM kai zhu <[hidden email]> wrote:
>
>
> actually, i admit i don't know what i'm talking about.  just generally confused (through ignorance) on how large-scale es-module dependencies resolve when loaded/imported asynchronously.
>
> On Wed, May 22, 2019 at 10:42 PM Logan Smyth <[hidden email]> wrote:
>
>
> Can you elaborate on what loading state you need to keep track of? What is the bottleneck that you run into? Also to be sure, when you say async-load, do you mean `import()`?
>
> On Wed, May 22, 2019, 20:17 kai zhu <[hidden email]> wrote:
>
>
> i don't use es-modules.
> but with amd/requirejs, I start having trouble with module-initializations in nodejs/browser at ~5 async modules (that may or may not have circular-references).  10 would be hard, and 20 would be near inhuman for me.
>
> can we say its somewhat impractical for most applications to load more than 50 async modules (with some of them having circular-references)?  and perhaps better design/spec module-loading mechanisms with this usability concern in mind?
>
> p.s. its also impractical for me to async-load 5 or more modules without using globalThis to keep track of each module's loading-state.
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
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Re: how many async-modules can js-app practically load?

kai zhu
i apologize for poor framing of my questions.  they are still formative, but i can clarify abit as follows:

1) original-question - is native es-module's async-behavior desirable?  async side-effects are difficult to manage -- i conjecture that async-loading 20 es-modules (with dependent side-effects) is not practical for most mortals to handle.
@frederick describes the mechanism for how to hint the brower to pre-fetch 20 es-modules. but if you pre-fetch, then is loading-behavior effectively synchronous?
@isiah says he has experience loading 50-100 modules, but was unclear whether they were individual [async] ```<script type="module">``` tags, or some es5-transpiled rollup.

i may be wrong about everything, as i'm a bit ignorant on what async actually means in es-modules (and appreciate it, if someone can clarify that).



2) the second-question about es-module rollups (which you and i are debating) stemmed from @isiah's response -- if he and everyone-else use es5-transpiled rollups (which i suspect), then shouldn't it be desirable for es-modules to natively support rollups as well?  currently, there's no way to natively rollup multiple es-modules into a single bundle.

this 2nd question also has implications about es-module's async-behavior (because rollups "load" modules in sync/blocking fashion).  this could change side-effect behaviors between development-mode (20 [async] ```<script type="module">``` tags) and production-mode (1 rollup-bundle).  again, i may be wrong about that, as i'm ignorant about what async actually is in es-modules.

-kai

On Sat, Jun 1, 2019 at 9:22 PM guest271314 <[hidden email]> wrote:
> it doesn't actually ```import``` 1000+ es-modules inside the rollup-file. it just creates one es-module that exports a dictionary -- and assigns the dictionary 1000+ vanilla json-objects and functions.

The code provides a means to fetch N resources and export those resources within a single object.

> currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
> in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.
>
> if we're actually committed to native es-modules, then we either
> 1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
> 2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

You still have not clearly defined what you mean by "rolled-up". That language appears to be a random nickname, not any immutable principle that individuals are bound to recognize or observe (even if "rolled-up" were some form of a coding style or standard).

Nor is it clear what you mean by "production". 

There is no external central committee that stamps code as "production". Even if there were no individual is obliged to submit to such a procedure nor have any concern for such an arbitrary and irrelevant presumptive review of code. 

The only observable points are input and output. In general, how output is achieved is immaterial. If there are specific restrictions as to how the output can be achieved then those restrictions need to be clearly defined. 



The original post asked "how many async-modules can js-app practically load?" and mentioned "circular-references" (the thread appears to mainly be about one or more coding styles, not code itself) though as yet no code has been posted which demonstrates "circular-references" or any other coding problem.

On Sun, Jun 2, 2019 at 1:30 AM kai zhu <[hidden email]> wrote:
i played around with your code in jsfiddle [1], and understand it a little more.
it doesn't actually ```import``` 1000+ es-modules inside the rollup-file.
it just creates one es-module that exports a dictionary
 -- and assigns the dictionary 1000+ vanilla json-objects and functions.

```js
// the "rollup-file" is a single es-module
// that exports 1000+ vanilla dictionary-entries
const modules = {};

// this is not a es-module, nor is it rolled-up (external fetch)
modules.image = <await fetch json from gist.github.com>

// this is not a [rolled-up] es-module
modules.fn = function () {...}

// these are not [rolled-up] es-modules
Object.assign(modules, <1000 json-entries>)

export {modules}
```

currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.

if we're actually committed to native es-modules, then we either
1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

```js
// rollup.js with [hypothetical] # delimited es-modules
# module aa
import {bb} as bb;
export ...;

# module bb
export ...;
```

i'm generally skeptical of option 1, given how poorly npmjs.com has handled similar problems deduplicating children in node_modules/ directory.

[1] jsfiddle pseudo-module rollup

On Sat, Jun 1, 2019 at 5:30 PM guest271314 <[hidden email]> wrote:
> your rollup solution is interesting, 

What  is "rollup" referring to? 

> but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  

The duplicate ("collision") entry an ```try..catch``` block is included in the code to demonstrate given an array of module names to be exported and imported as identifiers 1) duplicate entries can be filtered; 2) if a plain object is exported duplicate identifiers ("collision") is not possible as a JavaScript plain object does not have duplicate property names ("collision"); if there is an issue with identifiers in a module the cause would not be the number of async-modules loaded ("how many"), but the naming of the identifiers within the code, using or not using ```const``` or ```let```. Still not sure what the actual issue is?

> don't completely understand how it works, 

Use an ```async``` function to fetch data, check for the described "collision" , create a ```data URI``` to be imported, optionally, append addition code to be executed within the ```<script type="module">```.

> but not sure of suitability for production-use, because of its dynamic <script> tag generation.

What is the issue with dynamic ```<script>``` tag generation? 

There is more than one possible approach to achieve the presumptive requirement, that is still not clear to the exclusion of what is not the expected result.

There were no restrictions described at the OP and following messages other than other than 

pure-es6 application with 20 es-modules rolled-up into one [production] bundle?

The example code uses only JavaScript implementation shipped with the browser without any external, third-party libraries.
 
What standard or definition are you relying for the meaning of the term "production-use"? What procedure are you using to determine if code is "production-use" "suitable"? How is that procedure related to "how many async-modules can js-app practically load?"?



On Sat, Jun 1, 2019 at 9:42 PM kai zhu <[hidden email]> wrote:
your rollup solution is interesting, but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  don't completely understand how it works, but not sure of suitability for production-use, because of its dynamic <script> tag generation.

```console
ReferenceError: module names ["yeqjqb02mvg3yze26rc5"] are not unique
    at data:application/javascript,%0A%20%20%20%20%20%20const%20modules...
```

On Sat, Jun 1, 2019 at 2:33 PM guest271314 <[hidden email]> wrote:
Re: how many async-modules can js-app practically load?

An example of exporting and importing loading 1000 properties in a single module, where duplicate property names are checked for. Since JavaScript plain objects cannot have duplicate property names there should not be any "collisions"; the code can check for and modify the object to be exported, though the last duplicate property name will be exported without any errors thrown unless the code is composed to throw such an error.

```
  (async() => {
    const oneThousandModules = encodeURIComponent(
      // substitute rand for a Set of module names to be exported
      // e.g. const moduleNames = ['moduleA', 'moduleB', ...moduleZ]
      `
      const modules = {};
      // set a function to be exported
      modules.fn = function() {return 'a function'};
      // function to set (1000) 'random' module names to be exported
      const rand = (seed = 'abcdefghijklmnopqrstuvwxyz0123456789', n = 5, len = seed.length) =>
        '.'.repeat(n).replace(/./g, _ => seed[~~(Math.random() * len)]);
        // use Set for unique module identifiers
        const moduleNames = [...Array(1000)].map(_ => rand());
        const moduleIdentifiers = new Set(moduleNames);
        // below line will cause ReferenceError to be thrown
        moduleNames.push(moduleNames[0]);
        try {
          if (moduleIdentifiers.size !== moduleNames.length) {
            // check for duplicates
            const duplicates = moduleNames.filter((moduleName, index) => moduleNames.indexOf(moduleName) !== index);
            // notification of duplicate module names
            throw new ReferenceError('module names ' + JSON.stringify(duplicates) + ' are not unique');
            // perform the designated task if duplicate module names are found here
          }
        } catch (e) {
          console.error(e);
          console.trace();
        }
        // get, set (sync or async) exported module here
        Object.assign(modules, ...[...moduleIdentifiers].map((id, value) => ({[id]:value})));
        // since JavaScript plain object cannot have duplicate property names
        // modules object will still be exported without duplicate property names
        // without collisions
        export {modules}
    `);
    const scriptText = `import {modules} from "data:application/javascript,${oneThousandModules};${encodeURIComponent('console.log(modules);for (const key in modules) {if (typeof modules[key] === \'function\') {console.log(modules[key]());}}')}"`;
    const script = document.createElement("script");
    script.type = "module";
    script.textContent = scriptText;
    document.head.appendChild(script);
  })();
```


On Sat, Jun 1, 2019 at 1:51 AM kai zhu <[hidden email]> wrote:
> Place all of the code to be exported in 1 file?  
 
that obviously will not work, because of module-scope collision.  can anyone share their experience on deploying a [babel-free] pure-es6 application with 20 es-modules rolled-up into one [production] bundle?  is it even possible?


On Fri, May 31, 2019 at 7:55 PM guest271314 <[hidden email]> wrote:
how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?

Place all of the code to be exported in 1 file? 

with some of them having circular-references

Not certain how that is possible when using ```import``` within ```<script type="module">```?

how many async-modules can js-app practically load?

Again, how many have you tried to load? 100? 500? 1000? Either should be possible.

What specific issue are you actually to resolve?

On Fri, May 31, 2019 at 5:40 PM kai zhu <[hidden email]> wrote:
> Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

was that with some combination of babel/rollup/webpack or pure-es6?
if i want to develop a pure-es6 webapp (no babel), how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?


On Fri, May 31, 2019 at 10:47 AM Isiah Meadows <[hidden email]> wrote:
If it's bundled by Rollup or Webpack into a single bundle, it's
equivalent to a single `<script type="module" src="...">` pointing
towards the original entry point, excluding network requests.* But in
either case, you aren't listing 50 scripts, you're only listing the
entry module and importing child modules within parent modules. Rollup
and Webpack do mostly the same thing browsers do when it comes to
resolving dependencies, just they generate a bundle afterwards where
browsers execute code afterwards. Also, it's worth noting that the gap
between a single large request and multiple smaller requests has
shrunk a lot since HTTP/2 came along, since it's binary, it allows
requests and response data to be interleaved, it better leverages the
underlying TCP protocol format, and it allows servers to send data
pre-emptively without the client requesting it first. (Web sockets are
built on this functionality.) It's still better to bundle in general,
but it's less of a problem not to.

This is *not* the case for `<script type="module">` elements - those
operate more like inline scripts that happen to have the ability to
`import`.

Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

* This is, of course, not the case if you are using pure ES6 and you
aren't using any plugins to, say, run the original source through
Babel for React + JSX or something.

-----

Isiah Meadows
[hidden email]
www.isiahmeadows.com
On Sat, May 25, 2019 at 2:12 AM kai zhu <[hidden email]> wrote:
>
> Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
>
> so async-loading 50 ```<script type="module">``` tags
> has equivalent side-effect
> as sync-loading single webpack-rollup (of same 50 modules)?
>
> i have nagging suspicion of doubts.  has anyone tried native async-loading large numbers (>10) of
> ```<script type="module">``` tags, and verify it resolves identically to using a single webpack-rollup?
>
> again, i'm not that knowledgeable on es-modules, so above question may be trivially true, and i'm just not aware.
>
> -kai
>
> On 24 May 2019, at 23:41, Isiah Meadows <[hidden email]> wrote:
>
> There's two main reasons why it scales:
>
> 1. Modules are strongly encapsulated while minimizing global pollution.
> 2. The resolution algorithm applies the same logic no matter how many
> modules are loaded.
>
> It's much easier for it to scale when you write the code unaware of
> how many modules you might be loading and unaware of how deep their
> dependency graph is. Fewer assumptions here is key. It's an
> engineering problem, but a relatively simple one.
>
> If you want a short example of how sync module resolution works, you
> can take a look at this little utility I wrote:
> https://github.com/isiahmeadows/simple-require-loader. That doesn't
> asynchronously resolve modules, but it should help explain the process
> from a synchronous standpoint. Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
> -----
>
> Isiah Meadows
> [hidden email]
> www.isiahmeadows.com
>
> On Thu, May 23, 2019 at 10:49 AM kai zhu <[hidden email]> wrote:
>
>
> actually, i admit i don't know what i'm talking about.  just generally confused (through ignorance) on how large-scale es-module dependencies resolve when loaded/imported asynchronously.
>
> On Wed, May 22, 2019 at 10:42 PM Logan Smyth <[hidden email]> wrote:
>
>
> Can you elaborate on what loading state you need to keep track of? What is the bottleneck that you run into? Also to be sure, when you say async-load, do you mean `import()`?
>
> On Wed, May 22, 2019, 20:17 kai zhu <[hidden email]> wrote:
>
>
> i don't use es-modules.
> but with amd/requirejs, I start having trouble with module-initializations in nodejs/browser at ~5 async modules (that may or may not have circular-references).  10 would be hard, and 20 would be near inhuman for me.
>
> can we say its somewhat impractical for most applications to load more than 50 async modules (with some of them having circular-references)?  and perhaps better design/spec module-loading mechanisms with this usability concern in mind?
>
> p.s. its also impractical for me to async-load 5 or more modules without using globalThis to keep track of each module's loading-state.
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
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Re: how many async-modules can js-app practically load?

guest271314
1) original-question - is native es-module's async-behavior desirable?  async side-effects are difficult to manage -- i conjecture that async-loading 20 es-modules (with dependent side-effects) is not practical for most mortals to handle.

It depends on what you mean by "desirable" in a given context. 

There is no difference from loading 1 module and loading 1000 modules except for network cost, memory and disk space usage. 

Mortals can handle far more than loading 20 es-modules. 

What are the specific  "side-effects" that you are referring to?

describes the mechanism for how to hint the brower to pre-fetch 20 es-modules. but if you pre-fetch, then is loading-behavior effectively synchronous?

Resources can be "pre-fetched" using various means. From caching the first request and using the cached data instead of making future requests for the same resources to storing one or more entire directories in the browser configuration folder using `requestFileSystem` (Chromiom/Chrome).

but was unclear whether they were individual [async] ```<script type="module">``` tags, or some es5-transpiled rollup

There should not be any difference between the two approaches. If there is a difference then you should be able to clearly state what the difference is, and demonstrate the difference by reproduction, without speculating and not demonstrating a difference by means of reproduction.

2) the second-question about es-module rollups (which you and i are debating) stemmed from @isiah's response -- if he and everyone-else use es5-transpiled rollups (which i suspect), 

Do not care what "everyone-else" is supposedly doing. How can you possibly know what everyone-else is doing and even if you did know what third-parties are doing how does that affect what you are doing?

then shouldn't it be desirable for es-modules to natively support rollups as well?  currently, there's no way to natively rollup multiple es-modules into a single bundle.

There are ways to "bundle" multiple modules into a single export "natively", as demonstrated at the previously posted code.

Another example approach

```
// sync
const o = {
  a:1, b:2, c:3
};
// async
const cities = fetch("https://gist.githubusercontent.com/guest271314/ffac94353ab16f42160e/raw/aaee70a3e351f6c7bc00178eabb5970a02df87e9/states.json")
               .then(response => response.json())
               .catch(e => {console.error(e); return "error fetching cities module"});
// async            
const video = fetch("https://upload.wikimedia.org/wikipedia/commons/d/d9/120-cell.ogv")
               .then(response => response.blob())
              .catch(e => {console.error(e); return "error fetching video module"});
// multiple "modules" exported
export {o, cities, video};
```

at single ```<script type="module">```

```
    <script type="module">
      import * as o from "./script.js";
      (async(mods) => {
        for (const [key, value] of mods) {
          if (value instanceof Promise) {
            console.log("async module", key, await value)
          } else {
            console.log("sync module", key, value);
          }
        }
      })(Object.entries(o));
    </script>
```

Still there is no actual problem statement. Rather, there is conjecture without a definitive issue to solve. 
 

 

On Sun, Jun 2, 2019 at 3:54 AM kai zhu <[hidden email]> wrote:
i apologize for poor framing of my questions.  they are still formative, but i can clarify abit as follows:

1) original-question - is native es-module's async-behavior desirable?  async side-effects are difficult to manage -- i conjecture that async-loading 20 es-modules (with dependent side-effects) is not practical for most mortals to handle.
@frederick describes the mechanism for how to hint the brower to pre-fetch 20 es-modules. but if you pre-fetch, then is loading-behavior effectively synchronous?
@isiah says he has experience loading 50-100 modules, but was unclear whether they were individual [async] ```<script type="module">``` tags, or some es5-transpiled rollup.

i may be wrong about everything, as i'm a bit ignorant on what async actually means in es-modules (and appreciate it, if someone can clarify that).



2) the second-question about es-module rollups (which you and i are debating) stemmed from @isiah's response -- if he and everyone-else use es5-transpiled rollups (which i suspect), then shouldn't it be desirable for es-modules to natively support rollups as well?  currently, there's no way to natively rollup multiple es-modules into a single bundle.

this 2nd question also has implications about es-module's async-behavior (because rollups "load" modules in sync/blocking fashion).  this could change side-effect behaviors between development-mode (20 [async] ```<script type="module">``` tags) and production-mode (1 rollup-bundle).  again, i may be wrong about that, as i'm ignorant about what async actually is in es-modules.

-kai

On Sat, Jun 1, 2019 at 9:22 PM guest271314 <[hidden email]> wrote:
> it doesn't actually ```import``` 1000+ es-modules inside the rollup-file. it just creates one es-module that exports a dictionary -- and assigns the dictionary 1000+ vanilla json-objects and functions.

The code provides a means to fetch N resources and export those resources within a single object.

> currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
> in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.
>
> if we're actually committed to native es-modules, then we either
> 1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
> 2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

You still have not clearly defined what you mean by "rolled-up". That language appears to be a random nickname, not any immutable principle that individuals are bound to recognize or observe (even if "rolled-up" were some form of a coding style or standard).

Nor is it clear what you mean by "production". 

There is no external central committee that stamps code as "production". Even if there were no individual is obliged to submit to such a procedure nor have any concern for such an arbitrary and irrelevant presumptive review of code. 

The only observable points are input and output. In general, how output is achieved is immaterial. If there are specific restrictions as to how the output can be achieved then those restrictions need to be clearly defined. 



The original post asked "how many async-modules can js-app practically load?" and mentioned "circular-references" (the thread appears to mainly be about one or more coding styles, not code itself) though as yet no code has been posted which demonstrates "circular-references" or any other coding problem.

On Sun, Jun 2, 2019 at 1:30 AM kai zhu <[hidden email]> wrote:
i played around with your code in jsfiddle [1], and understand it a little more.
it doesn't actually ```import``` 1000+ es-modules inside the rollup-file.
it just creates one es-module that exports a dictionary
 -- and assigns the dictionary 1000+ vanilla json-objects and functions.

```js
// the "rollup-file" is a single es-module
// that exports 1000+ vanilla dictionary-entries
const modules = {};

// this is not a es-module, nor is it rolled-up (external fetch)
modules.image = <await fetch json from gist.github.com>

// this is not a [rolled-up] es-module
modules.fn = function () {...}

// these are not [rolled-up] es-modules
Object.assign(modules, <1000 json-entries>)

export {modules}
```

currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.

if we're actually committed to native es-modules, then we either
1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

```js
// rollup.js with [hypothetical] # delimited es-modules
# module aa
import {bb} as bb;
export ...;

# module bb
export ...;
```

i'm generally skeptical of option 1, given how poorly npmjs.com has handled similar problems deduplicating children in node_modules/ directory.

[1] jsfiddle pseudo-module rollup

On Sat, Jun 1, 2019 at 5:30 PM guest271314 <[hidden email]> wrote:
> your rollup solution is interesting, 

What  is "rollup" referring to? 

> but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  

The duplicate ("collision") entry an ```try..catch``` block is included in the code to demonstrate given an array of module names to be exported and imported as identifiers 1) duplicate entries can be filtered; 2) if a plain object is exported duplicate identifiers ("collision") is not possible as a JavaScript plain object does not have duplicate property names ("collision"); if there is an issue with identifiers in a module the cause would not be the number of async-modules loaded ("how many"), but the naming of the identifiers within the code, using or not using ```const``` or ```let```. Still not sure what the actual issue is?

> don't completely understand how it works, 

Use an ```async``` function to fetch data, check for the described "collision" , create a ```data URI``` to be imported, optionally, append addition code to be executed within the ```<script type="module">```.

> but not sure of suitability for production-use, because of its dynamic <script> tag generation.

What is the issue with dynamic ```<script>``` tag generation? 

There is more than one possible approach to achieve the presumptive requirement, that is still not clear to the exclusion of what is not the expected result.

There were no restrictions described at the OP and following messages other than other than 

pure-es6 application with 20 es-modules rolled-up into one [production] bundle?

The example code uses only JavaScript implementation shipped with the browser without any external, third-party libraries.
 
What standard or definition are you relying for the meaning of the term "production-use"? What procedure are you using to determine if code is "production-use" "suitable"? How is that procedure related to "how many async-modules can js-app practically load?"?



On Sat, Jun 1, 2019 at 9:42 PM kai zhu <[hidden email]> wrote:
your rollup solution is interesting, but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  don't completely understand how it works, but not sure of suitability for production-use, because of its dynamic <script> tag generation.

```console
ReferenceError: module names ["yeqjqb02mvg3yze26rc5"] are not unique
    at data:application/javascript,%0A%20%20%20%20%20%20const%20modules...
```

On Sat, Jun 1, 2019 at 2:33 PM guest271314 <[hidden email]> wrote:
Re: how many async-modules can js-app practically load?

An example of exporting and importing loading 1000 properties in a single module, where duplicate property names are checked for. Since JavaScript plain objects cannot have duplicate property names there should not be any "collisions"; the code can check for and modify the object to be exported, though the last duplicate property name will be exported without any errors thrown unless the code is composed to throw such an error.

```
  (async() => {
    const oneThousandModules = encodeURIComponent(
      // substitute rand for a Set of module names to be exported
      // e.g. const moduleNames = ['moduleA', 'moduleB', ...moduleZ]
      `
      const modules = {};
      // set a function to be exported
      modules.fn = function() {return 'a function'};
      // function to set (1000) 'random' module names to be exported
      const rand = (seed = 'abcdefghijklmnopqrstuvwxyz0123456789', n = 5, len = seed.length) =>
        '.'.repeat(n).replace(/./g, _ => seed[~~(Math.random() * len)]);
        // use Set for unique module identifiers
        const moduleNames = [...Array(1000)].map(_ => rand());
        const moduleIdentifiers = new Set(moduleNames);
        // below line will cause ReferenceError to be thrown
        moduleNames.push(moduleNames[0]);
        try {
          if (moduleIdentifiers.size !== moduleNames.length) {
            // check for duplicates
            const duplicates = moduleNames.filter((moduleName, index) => moduleNames.indexOf(moduleName) !== index);
            // notification of duplicate module names
            throw new ReferenceError('module names ' + JSON.stringify(duplicates) + ' are not unique');
            // perform the designated task if duplicate module names are found here
          }
        } catch (e) {
          console.error(e);
          console.trace();
        }
        // get, set (sync or async) exported module here
        Object.assign(modules, ...[...moduleIdentifiers].map((id, value) => ({[id]:value})));
        // since JavaScript plain object cannot have duplicate property names
        // modules object will still be exported without duplicate property names
        // without collisions
        export {modules}
    `);
    const scriptText = `import {modules} from "data:application/javascript,${oneThousandModules};${encodeURIComponent('console.log(modules);for (const key in modules) {if (typeof modules[key] === \'function\') {console.log(modules[key]());}}')}"`;
    const script = document.createElement("script");
    script.type = "module";
    script.textContent = scriptText;
    document.head.appendChild(script);
  })();
```


On Sat, Jun 1, 2019 at 1:51 AM kai zhu <[hidden email]> wrote:
> Place all of the code to be exported in 1 file?  
 
that obviously will not work, because of module-scope collision.  can anyone share their experience on deploying a [babel-free] pure-es6 application with 20 es-modules rolled-up into one [production] bundle?  is it even possible?


On Fri, May 31, 2019 at 7:55 PM guest271314 <[hidden email]> wrote:
how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?

Place all of the code to be exported in 1 file? 

with some of them having circular-references

Not certain how that is possible when using ```import``` within ```<script type="module">```?

how many async-modules can js-app practically load?

Again, how many have you tried to load? 100? 500? 1000? Either should be possible.

What specific issue are you actually to resolve?

On Fri, May 31, 2019 at 5:40 PM kai zhu <[hidden email]> wrote:
> Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

was that with some combination of babel/rollup/webpack or pure-es6?
if i want to develop a pure-es6 webapp (no babel), how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?


On Fri, May 31, 2019 at 10:47 AM Isiah Meadows <[hidden email]> wrote:
If it's bundled by Rollup or Webpack into a single bundle, it's
equivalent to a single `<script type="module" src="...">` pointing
towards the original entry point, excluding network requests.* But in
either case, you aren't listing 50 scripts, you're only listing the
entry module and importing child modules within parent modules. Rollup
and Webpack do mostly the same thing browsers do when it comes to
resolving dependencies, just they generate a bundle afterwards where
browsers execute code afterwards. Also, it's worth noting that the gap
between a single large request and multiple smaller requests has
shrunk a lot since HTTP/2 came along, since it's binary, it allows
requests and response data to be interleaved, it better leverages the
underlying TCP protocol format, and it allows servers to send data
pre-emptively without the client requesting it first. (Web sockets are
built on this functionality.) It's still better to bundle in general,
but it's less of a problem not to.

This is *not* the case for `<script type="module">` elements - those
operate more like inline scripts that happen to have the ability to
`import`.

Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

* This is, of course, not the case if you are using pure ES6 and you
aren't using any plugins to, say, run the original source through
Babel for React + JSX or something.

-----

Isiah Meadows
[hidden email]
www.isiahmeadows.com
On Sat, May 25, 2019 at 2:12 AM kai zhu <[hidden email]> wrote:
>
> Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
>
> so async-loading 50 ```<script type="module">``` tags
> has equivalent side-effect
> as sync-loading single webpack-rollup (of same 50 modules)?
>
> i have nagging suspicion of doubts.  has anyone tried native async-loading large numbers (>10) of
> ```<script type="module">``` tags, and verify it resolves identically to using a single webpack-rollup?
>
> again, i'm not that knowledgeable on es-modules, so above question may be trivially true, and i'm just not aware.
>
> -kai
>
> On 24 May 2019, at 23:41, Isiah Meadows <[hidden email]> wrote:
>
> There's two main reasons why it scales:
>
> 1. Modules are strongly encapsulated while minimizing global pollution.
> 2. The resolution algorithm applies the same logic no matter how many
> modules are loaded.
>
> It's much easier for it to scale when you write the code unaware of
> how many modules you might be loading and unaware of how deep their
> dependency graph is. Fewer assumptions here is key. It's an
> engineering problem, but a relatively simple one.
>
> If you want a short example of how sync module resolution works, you
> can take a look at this little utility I wrote:
> https://github.com/isiahmeadows/simple-require-loader. That doesn't
> asynchronously resolve modules, but it should help explain the process
> from a synchronous standpoint. Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
> -----
>
> Isiah Meadows
> [hidden email]
> www.isiahmeadows.com
>
> On Thu, May 23, 2019 at 10:49 AM kai zhu <[hidden email]> wrote:
>
>
> actually, i admit i don't know what i'm talking about.  just generally confused (through ignorance) on how large-scale es-module dependencies resolve when loaded/imported asynchronously.
>
> On Wed, May 22, 2019 at 10:42 PM Logan Smyth <[hidden email]> wrote:
>
>
> Can you elaborate on what loading state you need to keep track of? What is the bottleneck that you run into? Also to be sure, when you say async-load, do you mean `import()`?
>
> On Wed, May 22, 2019, 20:17 kai zhu <[hidden email]> wrote:
>
>
> i don't use es-modules.
> but with amd/requirejs, I start having trouble with module-initializations in nodejs/browser at ~5 async modules (that may or may not have circular-references).  10 would be hard, and 20 would be near inhuman for me.
>
> can we say its somewhat impractical for most applications to load more than 50 async modules (with some of them having circular-references)?  and perhaps better design/spec module-loading mechanisms with this usability concern in mind?
>
> p.s. its also impractical for me to async-load 5 or more modules without using globalThis to keep track of each module's loading-state.
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
_______________________________________________
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Re: how many async-modules can js-app practically load?

kai zhu
[hidden email], your example again is not a [native] bundle of two or more inlined es-modules.  its just a single es-module that that fetches json data.

i'm asking if its desirable to inline multiple es-modules into a single file natively, e.g.:

```
/*
 * es-module.rollup.js
 * this [hypothetical] rollup-file contains multiple inlined es-modules
 * to improve load-performance in production-deployment.
 */

// 1. inlined es-module ./main.js
import { foo } from "./counter.js"
import { bar } from "./display.js"
foo(bar);

// 2. inlined es-module ./counter.js
var foo;
foo = function (bar) {
    bar();
};
export { foo }

// 3. inlined es-module ./display.js
var bar;
bar = function () {
    console.log("hello world");
};
export { bar }
```

this native es-module inline-capability may not be desirable to you, which is fine.  it would be a datapoint against this feature (and rely instead on pre-emptive import-maps and http2-push, as explained by @frederick and @isiah).


On Sun, Jun 2, 2019 at 11:22 AM guest271314 <[hidden email]> wrote:
1) original-question - is native es-module's async-behavior desirable?  async side-effects are difficult to manage -- i conjecture that async-loading 20 es-modules (with dependent side-effects) is not practical for most mortals to handle.

It depends on what you mean by "desirable" in a given context. 

There is no difference from loading 1 module and loading 1000 modules except for network cost, memory and disk space usage. 

Mortals can handle far more than loading 20 es-modules. 

What are the specific  "side-effects" that you are referring to?

describes the mechanism for how to hint the brower to pre-fetch 20 es-modules. but if you pre-fetch, then is loading-behavior effectively synchronous?

Resources can be "pre-fetched" using various means. From caching the first request and using the cached data instead of making future requests for the same resources to storing one or more entire directories in the browser configuration folder using `requestFileSystem` (Chromiom/Chrome).

but was unclear whether they were individual [async] ```<script type="module">``` tags, or some es5-transpiled rollup

There should not be any difference between the two approaches. If there is a difference then you should be able to clearly state what the difference is, and demonstrate the difference by reproduction, without speculating and not demonstrating a difference by means of reproduction.

2) the second-question about es-module rollups (which you and i are debating) stemmed from @isiah's response -- if he and everyone-else use es5-transpiled rollups (which i suspect), 

Do not care what "everyone-else" is supposedly doing. How can you possibly know what everyone-else is doing and even if you did know what third-parties are doing how does that affect what you are doing?

then shouldn't it be desirable for es-modules to natively support rollups as well?  currently, there's no way to natively rollup multiple es-modules into a single bundle.

There are ways to "bundle" multiple modules into a single export "natively", as demonstrated at the previously posted code.

Another example approach

```
// sync
const o = {
  a:1, b:2, c:3
};
// async
const cities = fetch("https://gist.githubusercontent.com/guest271314/ffac94353ab16f42160e/raw/aaee70a3e351f6c7bc00178eabb5970a02df87e9/states.json")
               .then(response => response.json())
               .catch(e => {console.error(e); return "error fetching cities module"});
// async            
const video = fetch("https://upload.wikimedia.org/wikipedia/commons/d/d9/120-cell.ogv")
               .then(response => response.blob())
              .catch(e => {console.error(e); return "error fetching video module"});
// multiple "modules" exported
export {o, cities, video};
```

at single ```<script type="module">```

```
    <script type="module">
      import * as o from "./script.js";
      (async(mods) => {
        for (const [key, value] of mods) {
          if (value instanceof Promise) {
            console.log("async module", key, await value)
          } else {
            console.log("sync module", key, value);
          }
        }
      })(Object.entries(o));
    </script>
```

Still there is no actual problem statement. Rather, there is conjecture without a definitive issue to solve. 
 

 

On Sun, Jun 2, 2019 at 3:54 AM kai zhu <[hidden email]> wrote:
i apologize for poor framing of my questions.  they are still formative, but i can clarify abit as follows:

1) original-question - is native es-module's async-behavior desirable?  async side-effects are difficult to manage -- i conjecture that async-loading 20 es-modules (with dependent side-effects) is not practical for most mortals to handle.
@frederick describes the mechanism for how to hint the brower to pre-fetch 20 es-modules. but if you pre-fetch, then is loading-behavior effectively synchronous?
@isiah says he has experience loading 50-100 modules, but was unclear whether they were individual [async] ```<script type="module">``` tags, or some es5-transpiled rollup.

i may be wrong about everything, as i'm a bit ignorant on what async actually means in es-modules (and appreciate it, if someone can clarify that).



2) the second-question about es-module rollups (which you and i are debating) stemmed from @isiah's response -- if he and everyone-else use es5-transpiled rollups (which i suspect), then shouldn't it be desirable for es-modules to natively support rollups as well?  currently, there's no way to natively rollup multiple es-modules into a single bundle.

this 2nd question also has implications about es-module's async-behavior (because rollups "load" modules in sync/blocking fashion).  this could change side-effect behaviors between development-mode (20 [async] ```<script type="module">``` tags) and production-mode (1 rollup-bundle).  again, i may be wrong about that, as i'm ignorant about what async actually is in es-modules.

-kai

On Sat, Jun 1, 2019 at 9:22 PM guest271314 <[hidden email]> wrote:
> it doesn't actually ```import``` 1000+ es-modules inside the rollup-file. it just creates one es-module that exports a dictionary -- and assigns the dictionary 1000+ vanilla json-objects and functions.

The code provides a means to fetch N resources and export those resources within a single object.

> currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
> in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.
>
> if we're actually committed to native es-modules, then we either
> 1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
> 2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

You still have not clearly defined what you mean by "rolled-up". That language appears to be a random nickname, not any immutable principle that individuals are bound to recognize or observe (even if "rolled-up" were some form of a coding style or standard).

Nor is it clear what you mean by "production". 

There is no external central committee that stamps code as "production". Even if there were no individual is obliged to submit to such a procedure nor have any concern for such an arbitrary and irrelevant presumptive review of code. 

The only observable points are input and output. In general, how output is achieved is immaterial. If there are specific restrictions as to how the output can be achieved then those restrictions need to be clearly defined. 



The original post asked "how many async-modules can js-app practically load?" and mentioned "circular-references" (the thread appears to mainly be about one or more coding styles, not code itself) though as yet no code has been posted which demonstrates "circular-references" or any other coding problem.

On Sun, Jun 2, 2019 at 1:30 AM kai zhu <[hidden email]> wrote:
i played around with your code in jsfiddle [1], and understand it a little more.
it doesn't actually ```import``` 1000+ es-modules inside the rollup-file.
it just creates one es-module that exports a dictionary
 -- and assigns the dictionary 1000+ vanilla json-objects and functions.

```js
// the "rollup-file" is a single es-module
// that exports 1000+ vanilla dictionary-entries
const modules = {};

// this is not a es-module, nor is it rolled-up (external fetch)
modules.image = <await fetch json from gist.github.com>

// this is not a [rolled-up] es-module
modules.fn = function () {...}

// these are not [rolled-up] es-modules
Object.assign(modules, <1000 json-entries>)

export {modules}
```

currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.

if we're actually committed to native es-modules, then we either
1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

```js
// rollup.js with [hypothetical] # delimited es-modules
# module aa
import {bb} as bb;
export ...;

# module bb
export ...;
```

i'm generally skeptical of option 1, given how poorly npmjs.com has handled similar problems deduplicating children in node_modules/ directory.

[1] jsfiddle pseudo-module rollup

On Sat, Jun 1, 2019 at 5:30 PM guest271314 <[hidden email]> wrote:
> your rollup solution is interesting, 

What  is "rollup" referring to? 

> but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  

The duplicate ("collision") entry an ```try..catch``` block is included in the code to demonstrate given an array of module names to be exported and imported as identifiers 1) duplicate entries can be filtered; 2) if a plain object is exported duplicate identifiers ("collision") is not possible as a JavaScript plain object does not have duplicate property names ("collision"); if there is an issue with identifiers in a module the cause would not be the number of async-modules loaded ("how many"), but the naming of the identifiers within the code, using or not using ```const``` or ```let```. Still not sure what the actual issue is?

> don't completely understand how it works, 

Use an ```async``` function to fetch data, check for the described "collision" , create a ```data URI``` to be imported, optionally, append addition code to be executed within the ```<script type="module">```.

> but not sure of suitability for production-use, because of its dynamic <script> tag generation.

What is the issue with dynamic ```<script>``` tag generation? 

There is more than one possible approach to achieve the presumptive requirement, that is still not clear to the exclusion of what is not the expected result.

There were no restrictions described at the OP and following messages other than other than 

pure-es6 application with 20 es-modules rolled-up into one [production] bundle?

The example code uses only JavaScript implementation shipped with the browser without any external, third-party libraries.
 
What standard or definition are you relying for the meaning of the term "production-use"? What procedure are you using to determine if code is "production-use" "suitable"? How is that procedure related to "how many async-modules can js-app practically load?"?



On Sat, Jun 1, 2019 at 9:42 PM kai zhu <[hidden email]> wrote:
your rollup solution is interesting, but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  don't completely understand how it works, but not sure of suitability for production-use, because of its dynamic <script> tag generation.

```console
ReferenceError: module names ["yeqjqb02mvg3yze26rc5"] are not unique
    at data:application/javascript,%0A%20%20%20%20%20%20const%20modules...
```

On Sat, Jun 1, 2019 at 2:33 PM guest271314 <[hidden email]> wrote:
Re: how many async-modules can js-app practically load?

An example of exporting and importing loading 1000 properties in a single module, where duplicate property names are checked for. Since JavaScript plain objects cannot have duplicate property names there should not be any "collisions"; the code can check for and modify the object to be exported, though the last duplicate property name will be exported without any errors thrown unless the code is composed to throw such an error.

```
  (async() => {
    const oneThousandModules = encodeURIComponent(
      // substitute rand for a Set of module names to be exported
      // e.g. const moduleNames = ['moduleA', 'moduleB', ...moduleZ]
      `
      const modules = {};
      // set a function to be exported
      modules.fn = function() {return 'a function'};
      // function to set (1000) 'random' module names to be exported
      const rand = (seed = 'abcdefghijklmnopqrstuvwxyz0123456789', n = 5, len = seed.length) =>
        '.'.repeat(n).replace(/./g, _ => seed[~~(Math.random() * len)]);
        // use Set for unique module identifiers
        const moduleNames = [...Array(1000)].map(_ => rand());
        const moduleIdentifiers = new Set(moduleNames);
        // below line will cause ReferenceError to be thrown
        moduleNames.push(moduleNames[0]);
        try {
          if (moduleIdentifiers.size !== moduleNames.length) {
            // check for duplicates
            const duplicates = moduleNames.filter((moduleName, index) => moduleNames.indexOf(moduleName) !== index);
            // notification of duplicate module names
            throw new ReferenceError('module names ' + JSON.stringify(duplicates) + ' are not unique');
            // perform the designated task if duplicate module names are found here
          }
        } catch (e) {
          console.error(e);
          console.trace();
        }
        // get, set (sync or async) exported module here
        Object.assign(modules, ...[...moduleIdentifiers].map((id, value) => ({[id]:value})));
        // since JavaScript plain object cannot have duplicate property names
        // modules object will still be exported without duplicate property names
        // without collisions
        export {modules}
    `);
    const scriptText = `import {modules} from "data:application/javascript,${oneThousandModules};${encodeURIComponent('console.log(modules);for (const key in modules) {if (typeof modules[key] === \'function\') {console.log(modules[key]());}}')}"`;
    const script = document.createElement("script");
    script.type = "module";
    script.textContent = scriptText;
    document.head.appendChild(script);
  })();
```


On Sat, Jun 1, 2019 at 1:51 AM kai zhu <[hidden email]> wrote:
> Place all of the code to be exported in 1 file?  
 
that obviously will not work, because of module-scope collision.  can anyone share their experience on deploying a [babel-free] pure-es6 application with 20 es-modules rolled-up into one [production] bundle?  is it even possible?


On Fri, May 31, 2019 at 7:55 PM guest271314 <[hidden email]> wrote:
how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?

Place all of the code to be exported in 1 file? 

with some of them having circular-references

Not certain how that is possible when using ```import``` within ```<script type="module">```?

how many async-modules can js-app practically load?

Again, how many have you tried to load? 100? 500? 1000? Either should be possible.

What specific issue are you actually to resolve?

On Fri, May 31, 2019 at 5:40 PM kai zhu <[hidden email]> wrote:
> Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

was that with some combination of babel/rollup/webpack or pure-es6?
if i want to develop a pure-es6 webapp (no babel), how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?


On Fri, May 31, 2019 at 10:47 AM Isiah Meadows <[hidden email]> wrote:
If it's bundled by Rollup or Webpack into a single bundle, it's
equivalent to a single `<script type="module" src="...">` pointing
towards the original entry point, excluding network requests.* But in
either case, you aren't listing 50 scripts, you're only listing the
entry module and importing child modules within parent modules. Rollup
and Webpack do mostly the same thing browsers do when it comes to
resolving dependencies, just they generate a bundle afterwards where
browsers execute code afterwards. Also, it's worth noting that the gap
between a single large request and multiple smaller requests has
shrunk a lot since HTTP/2 came along, since it's binary, it allows
requests and response data to be interleaved, it better leverages the
underlying TCP protocol format, and it allows servers to send data
pre-emptively without the client requesting it first. (Web sockets are
built on this functionality.) It's still better to bundle in general,
but it's less of a problem not to.

This is *not* the case for `<script type="module">` elements - those
operate more like inline scripts that happen to have the ability to
`import`.

Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

* This is, of course, not the case if you are using pure ES6 and you
aren't using any plugins to, say, run the original source through
Babel for React + JSX or something.

-----

Isiah Meadows
[hidden email]
www.isiahmeadows.com
On Sat, May 25, 2019 at 2:12 AM kai zhu <[hidden email]> wrote:
>
> Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
>
> so async-loading 50 ```<script type="module">``` tags
> has equivalent side-effect
> as sync-loading single webpack-rollup (of same 50 modules)?
>
> i have nagging suspicion of doubts.  has anyone tried native async-loading large numbers (>10) of
> ```<script type="module">``` tags, and verify it resolves identically to using a single webpack-rollup?
>
> again, i'm not that knowledgeable on es-modules, so above question may be trivially true, and i'm just not aware.
>
> -kai
>
> On 24 May 2019, at 23:41, Isiah Meadows <[hidden email]> wrote:
>
> There's two main reasons why it scales:
>
> 1. Modules are strongly encapsulated while minimizing global pollution.
> 2. The resolution algorithm applies the same logic no matter how many
> modules are loaded.
>
> It's much easier for it to scale when you write the code unaware of
> how many modules you might be loading and unaware of how deep their
> dependency graph is. Fewer assumptions here is key. It's an
> engineering problem, but a relatively simple one.
>
> If you want a short example of how sync module resolution works, you
> can take a look at this little utility I wrote:
> https://github.com/isiahmeadows/simple-require-loader. That doesn't
> asynchronously resolve modules, but it should help explain the process
> from a synchronous standpoint. Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
> -----
>
> Isiah Meadows
> [hidden email]
> www.isiahmeadows.com
>
> On Thu, May 23, 2019 at 10:49 AM kai zhu <[hidden email]> wrote:
>
>
> actually, i admit i don't know what i'm talking about.  just generally confused (through ignorance) on how large-scale es-module dependencies resolve when loaded/imported asynchronously.
>
> On Wed, May 22, 2019 at 10:42 PM Logan Smyth <[hidden email]> wrote:
>
>
> Can you elaborate on what loading state you need to keep track of? What is the bottleneck that you run into? Also to be sure, when you say async-load, do you mean `import()`?
>
> On Wed, May 22, 2019, 20:17 kai zhu <[hidden email]> wrote:
>
>
> i don't use es-modules.
> but with amd/requirejs, I start having trouble with module-initializations in nodejs/browser at ~5 async modules (that may or may not have circular-references).  10 would be hard, and 20 would be near inhuman for me.
>
> can we say its somewhat impractical for most applications to load more than 50 async modules (with some of them having circular-references)?  and perhaps better design/spec module-loading mechanisms with this usability concern in mind?
>
> p.s. its also impractical for me to async-load 5 or more modules without using globalThis to keep track of each module's loading-state.
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
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Re: how many async-modules can js-app practically load?

guest271314
Multiple imports are already possible

```
import {inline} from "./inline.js";
import {nextInline} from "./nextInline.js";

const o = {
  a:1, b:2, c:3
};

// ...

export {o, cities, video, inline, nextInline};
```

Are you proposing multiple ```export```s?

```
export {o, cities, video, inline, nextInline};
o.c = 7;
export {o};
```



On Sun, Jun 2, 2019 at 6:19 PM kai zhu <[hidden email]> wrote:
[hidden email], your example again is not a [native] bundle of two or more inlined es-modules.  its just a single es-module that that fetches json data.

i'm asking if its desirable to inline multiple es-modules into a single file natively, e.g.:

```
/*
 * es-module.rollup.js
 * this [hypothetical] rollup-file contains multiple inlined es-modules
 * to improve load-performance in production-deployment.
 */

// 1. inlined es-module ./main.js
import { foo } from "./counter.js"
import { bar } from "./display.js"
foo(bar);

// 2. inlined es-module ./counter.js
var foo;
foo = function (bar) {
    bar();
};
export { foo }

// 3. inlined es-module ./display.js
var bar;
bar = function () {
    console.log("hello world");
};
export { bar }
```

this native es-module inline-capability may not be desirable to you, which is fine.  it would be a datapoint against this feature (and rely instead on pre-emptive import-maps and http2-push, as explained by @frederick and @isiah).


On Sun, Jun 2, 2019 at 11:22 AM guest271314 <[hidden email]> wrote:
1) original-question - is native es-module's async-behavior desirable?  async side-effects are difficult to manage -- i conjecture that async-loading 20 es-modules (with dependent side-effects) is not practical for most mortals to handle.

It depends on what you mean by "desirable" in a given context. 

There is no difference from loading 1 module and loading 1000 modules except for network cost, memory and disk space usage. 

Mortals can handle far more than loading 20 es-modules. 

What are the specific  "side-effects" that you are referring to?

describes the mechanism for how to hint the brower to pre-fetch 20 es-modules. but if you pre-fetch, then is loading-behavior effectively synchronous?

Resources can be "pre-fetched" using various means. From caching the first request and using the cached data instead of making future requests for the same resources to storing one or more entire directories in the browser configuration folder using `requestFileSystem` (Chromiom/Chrome).

but was unclear whether they were individual [async] ```<script type="module">``` tags, or some es5-transpiled rollup

There should not be any difference between the two approaches. If there is a difference then you should be able to clearly state what the difference is, and demonstrate the difference by reproduction, without speculating and not demonstrating a difference by means of reproduction.

2) the second-question about es-module rollups (which you and i are debating) stemmed from @isiah's response -- if he and everyone-else use es5-transpiled rollups (which i suspect), 

Do not care what "everyone-else" is supposedly doing. How can you possibly know what everyone-else is doing and even if you did know what third-parties are doing how does that affect what you are doing?

then shouldn't it be desirable for es-modules to natively support rollups as well?  currently, there's no way to natively rollup multiple es-modules into a single bundle.

There are ways to "bundle" multiple modules into a single export "natively", as demonstrated at the previously posted code.

Another example approach

```
// sync
const o = {
  a:1, b:2, c:3
};
// async
const cities = fetch("https://gist.githubusercontent.com/guest271314/ffac94353ab16f42160e/raw/aaee70a3e351f6c7bc00178eabb5970a02df87e9/states.json")
               .then(response => response.json())
               .catch(e => {console.error(e); return "error fetching cities module"});
// async            
const video = fetch("https://upload.wikimedia.org/wikipedia/commons/d/d9/120-cell.ogv")
               .then(response => response.blob())
              .catch(e => {console.error(e); return "error fetching video module"});
// multiple "modules" exported
export {o, cities, video};
```

at single ```<script type="module">```

```
    <script type="module">
      import * as o from "./script.js";
      (async(mods) => {
        for (const [key, value] of mods) {
          if (value instanceof Promise) {
            console.log("async module", key, await value)
          } else {
            console.log("sync module", key, value);
          }
        }
      })(Object.entries(o));
    </script>
```

Still there is no actual problem statement. Rather, there is conjecture without a definitive issue to solve. 
 

 

On Sun, Jun 2, 2019 at 3:54 AM kai zhu <[hidden email]> wrote:
i apologize for poor framing of my questions.  they are still formative, but i can clarify abit as follows:

1) original-question - is native es-module's async-behavior desirable?  async side-effects are difficult to manage -- i conjecture that async-loading 20 es-modules (with dependent side-effects) is not practical for most mortals to handle.
@frederick describes the mechanism for how to hint the brower to pre-fetch 20 es-modules. but if you pre-fetch, then is loading-behavior effectively synchronous?
@isiah says he has experience loading 50-100 modules, but was unclear whether they were individual [async] ```<script type="module">``` tags, or some es5-transpiled rollup.

i may be wrong about everything, as i'm a bit ignorant on what async actually means in es-modules (and appreciate it, if someone can clarify that).



2) the second-question about es-module rollups (which you and i are debating) stemmed from @isiah's response -- if he and everyone-else use es5-transpiled rollups (which i suspect), then shouldn't it be desirable for es-modules to natively support rollups as well?  currently, there's no way to natively rollup multiple es-modules into a single bundle.

this 2nd question also has implications about es-module's async-behavior (because rollups "load" modules in sync/blocking fashion).  this could change side-effect behaviors between development-mode (20 [async] ```<script type="module">``` tags) and production-mode (1 rollup-bundle).  again, i may be wrong about that, as i'm ignorant about what async actually is in es-modules.

-kai

On Sat, Jun 1, 2019 at 9:22 PM guest271314 <[hidden email]> wrote:
> it doesn't actually ```import``` 1000+ es-modules inside the rollup-file. it just creates one es-module that exports a dictionary -- and assigns the dictionary 1000+ vanilla json-objects and functions.

The code provides a means to fetch N resources and export those resources within a single object.

> currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
> in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.
>
> if we're actually committed to native es-modules, then we either
> 1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
> 2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

You still have not clearly defined what you mean by "rolled-up". That language appears to be a random nickname, not any immutable principle that individuals are bound to recognize or observe (even if "rolled-up" were some form of a coding style or standard).

Nor is it clear what you mean by "production". 

There is no external central committee that stamps code as "production". Even if there were no individual is obliged to submit to such a procedure nor have any concern for such an arbitrary and irrelevant presumptive review of code. 

The only observable points are input and output. In general, how output is achieved is immaterial. If there are specific restrictions as to how the output can be achieved then those restrictions need to be clearly defined. 



The original post asked "how many async-modules can js-app practically load?" and mentioned "circular-references" (the thread appears to mainly be about one or more coding styles, not code itself) though as yet no code has been posted which demonstrates "circular-references" or any other coding problem.

On Sun, Jun 2, 2019 at 1:30 AM kai zhu <[hidden email]> wrote:
i played around with your code in jsfiddle [1], and understand it a little more.
it doesn't actually ```import``` 1000+ es-modules inside the rollup-file.
it just creates one es-module that exports a dictionary
 -- and assigns the dictionary 1000+ vanilla json-objects and functions.

```js
// the "rollup-file" is a single es-module
// that exports 1000+ vanilla dictionary-entries
const modules = {};

// this is not a es-module, nor is it rolled-up (external fetch)
modules.image = <await fetch json from gist.github.com>

// this is not a [rolled-up] es-module
modules.fn = function () {...}

// these are not [rolled-up] es-modules
Object.assign(modules, <1000 json-entries>)

export {modules}
```

currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.

if we're actually committed to native es-modules, then we either
1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

```js
// rollup.js with [hypothetical] # delimited es-modules
# module aa
import {bb} as bb;
export ...;

# module bb
export ...;
```

i'm generally skeptical of option 1, given how poorly npmjs.com has handled similar problems deduplicating children in node_modules/ directory.

[1] jsfiddle pseudo-module rollup

On Sat, Jun 1, 2019 at 5:30 PM guest271314 <[hidden email]> wrote:
> your rollup solution is interesting, 

What  is "rollup" referring to? 

> but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  

The duplicate ("collision") entry an ```try..catch``` block is included in the code to demonstrate given an array of module names to be exported and imported as identifiers 1) duplicate entries can be filtered; 2) if a plain object is exported duplicate identifiers ("collision") is not possible as a JavaScript plain object does not have duplicate property names ("collision"); if there is an issue with identifiers in a module the cause would not be the number of async-modules loaded ("how many"), but the naming of the identifiers within the code, using or not using ```const``` or ```let```. Still not sure what the actual issue is?

> don't completely understand how it works, 

Use an ```async``` function to fetch data, check for the described "collision" , create a ```data URI``` to be imported, optionally, append addition code to be executed within the ```<script type="module">```.

> but not sure of suitability for production-use, because of its dynamic <script> tag generation.

What is the issue with dynamic ```<script>``` tag generation? 

There is more than one possible approach to achieve the presumptive requirement, that is still not clear to the exclusion of what is not the expected result.

There were no restrictions described at the OP and following messages other than other than 

pure-es6 application with 20 es-modules rolled-up into one [production] bundle?

The example code uses only JavaScript implementation shipped with the browser without any external, third-party libraries.
 
What standard or definition are you relying for the meaning of the term "production-use"? What procedure are you using to determine if code is "production-use" "suitable"? How is that procedure related to "how many async-modules can js-app practically load?"?



On Sat, Jun 1, 2019 at 9:42 PM kai zhu <[hidden email]> wrote:
your rollup solution is interesting, but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  don't completely understand how it works, but not sure of suitability for production-use, because of its dynamic <script> tag generation.

```console
ReferenceError: module names ["yeqjqb02mvg3yze26rc5"] are not unique
    at data:application/javascript,%0A%20%20%20%20%20%20const%20modules...
```

On Sat, Jun 1, 2019 at 2:33 PM guest271314 <[hidden email]> wrote:
Re: how many async-modules can js-app practically load?

An example of exporting and importing loading 1000 properties in a single module, where duplicate property names are checked for. Since JavaScript plain objects cannot have duplicate property names there should not be any "collisions"; the code can check for and modify the object to be exported, though the last duplicate property name will be exported without any errors thrown unless the code is composed to throw such an error.

```
  (async() => {
    const oneThousandModules = encodeURIComponent(
      // substitute rand for a Set of module names to be exported
      // e.g. const moduleNames = ['moduleA', 'moduleB', ...moduleZ]
      `
      const modules = {};
      // set a function to be exported
      modules.fn = function() {return 'a function'};
      // function to set (1000) 'random' module names to be exported
      const rand = (seed = 'abcdefghijklmnopqrstuvwxyz0123456789', n = 5, len = seed.length) =>
        '.'.repeat(n).replace(/./g, _ => seed[~~(Math.random() * len)]);
        // use Set for unique module identifiers
        const moduleNames = [...Array(1000)].map(_ => rand());
        const moduleIdentifiers = new Set(moduleNames);
        // below line will cause ReferenceError to be thrown
        moduleNames.push(moduleNames[0]);
        try {
          if (moduleIdentifiers.size !== moduleNames.length) {
            // check for duplicates
            const duplicates = moduleNames.filter((moduleName, index) => moduleNames.indexOf(moduleName) !== index);
            // notification of duplicate module names
            throw new ReferenceError('module names ' + JSON.stringify(duplicates) + ' are not unique');
            // perform the designated task if duplicate module names are found here
          }
        } catch (e) {
          console.error(e);
          console.trace();
        }
        // get, set (sync or async) exported module here
        Object.assign(modules, ...[...moduleIdentifiers].map((id, value) => ({[id]:value})));
        // since JavaScript plain object cannot have duplicate property names
        // modules object will still be exported without duplicate property names
        // without collisions
        export {modules}
    `);
    const scriptText = `import {modules} from "data:application/javascript,${oneThousandModules};${encodeURIComponent('console.log(modules);for (const key in modules) {if (typeof modules[key] === \'function\') {console.log(modules[key]());}}')}"`;
    const script = document.createElement("script");
    script.type = "module";
    script.textContent = scriptText;
    document.head.appendChild(script);
  })();
```


On Sat, Jun 1, 2019 at 1:51 AM kai zhu <[hidden email]> wrote:
> Place all of the code to be exported in 1 file?  
 
that obviously will not work, because of module-scope collision.  can anyone share their experience on deploying a [babel-free] pure-es6 application with 20 es-modules rolled-up into one [production] bundle?  is it even possible?


On Fri, May 31, 2019 at 7:55 PM guest271314 <[hidden email]> wrote:
how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?

Place all of the code to be exported in 1 file? 

with some of them having circular-references

Not certain how that is possible when using ```import``` within ```<script type="module">```?

how many async-modules can js-app practically load?

Again, how many have you tried to load? 100? 500? 1000? Either should be possible.

What specific issue are you actually to resolve?

On Fri, May 31, 2019 at 5:40 PM kai zhu <[hidden email]> wrote:
> Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

was that with some combination of babel/rollup/webpack or pure-es6?
if i want to develop a pure-es6 webapp (no babel), how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?


On Fri, May 31, 2019 at 10:47 AM Isiah Meadows <[hidden email]> wrote:
If it's bundled by Rollup or Webpack into a single bundle, it's
equivalent to a single `<script type="module" src="...">` pointing
towards the original entry point, excluding network requests.* But in
either case, you aren't listing 50 scripts, you're only listing the
entry module and importing child modules within parent modules. Rollup
and Webpack do mostly the same thing browsers do when it comes to
resolving dependencies, just they generate a bundle afterwards where
browsers execute code afterwards. Also, it's worth noting that the gap
between a single large request and multiple smaller requests has
shrunk a lot since HTTP/2 came along, since it's binary, it allows
requests and response data to be interleaved, it better leverages the
underlying TCP protocol format, and it allows servers to send data
pre-emptively without the client requesting it first. (Web sockets are
built on this functionality.) It's still better to bundle in general,
but it's less of a problem not to.

This is *not* the case for `<script type="module">` elements - those
operate more like inline scripts that happen to have the ability to
`import`.

Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

* This is, of course, not the case if you are using pure ES6 and you
aren't using any plugins to, say, run the original source through
Babel for React + JSX or something.

-----

Isiah Meadows
[hidden email]
www.isiahmeadows.com
On Sat, May 25, 2019 at 2:12 AM kai zhu <[hidden email]> wrote:
>
> Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
>
> so async-loading 50 ```<script type="module">``` tags
> has equivalent side-effect
> as sync-loading single webpack-rollup (of same 50 modules)?
>
> i have nagging suspicion of doubts.  has anyone tried native async-loading large numbers (>10) of
> ```<script type="module">``` tags, and verify it resolves identically to using a single webpack-rollup?
>
> again, i'm not that knowledgeable on es-modules, so above question may be trivially true, and i'm just not aware.
>
> -kai
>
> On 24 May 2019, at 23:41, Isiah Meadows <[hidden email]> wrote:
>
> There's two main reasons why it scales:
>
> 1. Modules are strongly encapsulated while minimizing global pollution.
> 2. The resolution algorithm applies the same logic no matter how many
> modules are loaded.
>
> It's much easier for it to scale when you write the code unaware of
> how many modules you might be loading and unaware of how deep their
> dependency graph is. Fewer assumptions here is key. It's an
> engineering problem, but a relatively simple one.
>
> If you want a short example of how sync module resolution works, you
> can take a look at this little utility I wrote:
> https://github.com/isiahmeadows/simple-require-loader. That doesn't
> asynchronously resolve modules, but it should help explain the process
> from a synchronous standpoint. Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
> -----
>
> Isiah Meadows
> [hidden email]
> www.isiahmeadows.com
>
> On Thu, May 23, 2019 at 10:49 AM kai zhu <[hidden email]> wrote:
>
>
> actually, i admit i don't know what i'm talking about.  just generally confused (through ignorance) on how large-scale es-module dependencies resolve when loaded/imported asynchronously.
>
> On Wed, May 22, 2019 at 10:42 PM Logan Smyth <[hidden email]> wrote:
>
>
> Can you elaborate on what loading state you need to keep track of? What is the bottleneck that you run into? Also to be sure, when you say async-load, do you mean `import()`?
>
> On Wed, May 22, 2019, 20:17 kai zhu <[hidden email]> wrote:
>
>
> i don't use es-modules.
> but with amd/requirejs, I start having trouble with module-initializations in nodejs/browser at ~5 async modules (that may or may not have circular-references).  10 would be hard, and 20 would be near inhuman for me.
>
> can we say its somewhat impractical for most applications to load more than 50 async modules (with some of them having circular-references)?  and perhaps better design/spec module-loading mechanisms with this usability concern in mind?
>
> p.s. its also impractical for me to async-load 5 or more modules without using globalThis to keep track of each module's loading-state.
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
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Re: how many async-modules can js-app practically load?

kai zhu
not inline multiple ```export```'s, but inline multiple module-scopes.

```js
/*
 * how do you inline the two es-modules below
 * with colliding `foo` and `bar` variables?
 *
 * you can't unless you introduce new language-syntax
 * to somehow delimit their scopes
 */

// [hypothethical] es-module-scope delimiter
# es-module-scope "./inline.js"

// module ./inline.js
import { foo } from "./aa.js"
const bar = { baz: foo };
export { bar };



// [hypothethical] es-module-scope delimiter
# es-module-scope ./nextinline.js

// module ./nextinline.js
import { foo } from "./bb.js"
const bar = { baz: foo };  
export { bar };
```

On Sun, Jun 2, 2019 at 2:54 PM guest271314 <[hidden email]> wrote:
Multiple imports are already possible

```
import {inline} from "./inline.js";
import {nextInline} from "./nextInline.js";

const o = {
  a:1, b:2, c:3
};

// ...

export {o, cities, video, inline, nextInline};
```

Are you proposing multiple ```export```s?

```
export {o, cities, video, inline, nextInline};
o.c = 7;
export {o};
```



On Sun, Jun 2, 2019 at 6:19 PM kai zhu <[hidden email]> wrote:
[hidden email], your example again is not a [native] bundle of two or more inlined es-modules.  its just a single es-module that that fetches json data.

i'm asking if its desirable to inline multiple es-modules into a single file natively, e.g.:

```
/*
 * es-module.rollup.js
 * this [hypothetical] rollup-file contains multiple inlined es-modules
 * to improve load-performance in production-deployment.
 */

// 1. inlined es-module ./main.js
import { foo } from "./counter.js"
import { bar } from "./display.js"
foo(bar);

// 2. inlined es-module ./counter.js
var foo;
foo = function (bar) {
    bar();
};
export { foo }

// 3. inlined es-module ./display.js
var bar;
bar = function () {
    console.log("hello world");
};
export { bar }
```

this native es-module inline-capability may not be desirable to you, which is fine.  it would be a datapoint against this feature (and rely instead on pre-emptive import-maps and http2-push, as explained by @frederick and @isiah).


On Sun, Jun 2, 2019 at 11:22 AM guest271314 <[hidden email]> wrote:
1) original-question - is native es-module's async-behavior desirable?  async side-effects are difficult to manage -- i conjecture that async-loading 20 es-modules (with dependent side-effects) is not practical for most mortals to handle.

It depends on what you mean by "desirable" in a given context. 

There is no difference from loading 1 module and loading 1000 modules except for network cost, memory and disk space usage. 

Mortals can handle far more than loading 20 es-modules. 

What are the specific  "side-effects" that you are referring to?

describes the mechanism for how to hint the brower to pre-fetch 20 es-modules. but if you pre-fetch, then is loading-behavior effectively synchronous?

Resources can be "pre-fetched" using various means. From caching the first request and using the cached data instead of making future requests for the same resources to storing one or more entire directories in the browser configuration folder using `requestFileSystem` (Chromiom/Chrome).

but was unclear whether they were individual [async] ```<script type="module">``` tags, or some es5-transpiled rollup

There should not be any difference between the two approaches. If there is a difference then you should be able to clearly state what the difference is, and demonstrate the difference by reproduction, without speculating and not demonstrating a difference by means of reproduction.

2) the second-question about es-module rollups (which you and i are debating) stemmed from @isiah's response -- if he and everyone-else use es5-transpiled rollups (which i suspect), 

Do not care what "everyone-else" is supposedly doing. How can you possibly know what everyone-else is doing and even if you did know what third-parties are doing how does that affect what you are doing?

then shouldn't it be desirable for es-modules to natively support rollups as well?  currently, there's no way to natively rollup multiple es-modules into a single bundle.

There are ways to "bundle" multiple modules into a single export "natively", as demonstrated at the previously posted code.

Another example approach

```
// sync
const o = {
  a:1, b:2, c:3
};
// async
const cities = fetch("https://gist.githubusercontent.com/guest271314/ffac94353ab16f42160e/raw/aaee70a3e351f6c7bc00178eabb5970a02df87e9/states.json")
               .then(response => response.json())
               .catch(e => {console.error(e); return "error fetching cities module"});
// async            
const video = fetch("https://upload.wikimedia.org/wikipedia/commons/d/d9/120-cell.ogv")
               .then(response => response.blob())
              .catch(e => {console.error(e); return "error fetching video module"});
// multiple "modules" exported
export {o, cities, video};
```

at single ```<script type="module">```

```
    <script type="module">
      import * as o from "./script.js";
      (async(mods) => {
        for (const [key, value] of mods) {
          if (value instanceof Promise) {
            console.log("async module", key, await value)
          } else {
            console.log("sync module", key, value);
          }
        }
      })(Object.entries(o));
    </script>
```

Still there is no actual problem statement. Rather, there is conjecture without a definitive issue to solve. 
 

 

On Sun, Jun 2, 2019 at 3:54 AM kai zhu <[hidden email]> wrote:
i apologize for poor framing of my questions.  they are still formative, but i can clarify abit as follows:

1) original-question - is native es-module's async-behavior desirable?  async side-effects are difficult to manage -- i conjecture that async-loading 20 es-modules (with dependent side-effects) is not practical for most mortals to handle.
@frederick describes the mechanism for how to hint the brower to pre-fetch 20 es-modules. but if you pre-fetch, then is loading-behavior effectively synchronous?
@isiah says he has experience loading 50-100 modules, but was unclear whether they were individual [async] ```<script type="module">``` tags, or some es5-transpiled rollup.

i may be wrong about everything, as i'm a bit ignorant on what async actually means in es-modules (and appreciate it, if someone can clarify that).



2) the second-question about es-module rollups (which you and i are debating) stemmed from @isiah's response -- if he and everyone-else use es5-transpiled rollups (which i suspect), then shouldn't it be desirable for es-modules to natively support rollups as well?  currently, there's no way to natively rollup multiple es-modules into a single bundle.

this 2nd question also has implications about es-module's async-behavior (because rollups "load" modules in sync/blocking fashion).  this could change side-effect behaviors between development-mode (20 [async] ```<script type="module">``` tags) and production-mode (1 rollup-bundle).  again, i may be wrong about that, as i'm ignorant about what async actually is in es-modules.

-kai

On Sat, Jun 1, 2019 at 9:22 PM guest271314 <[hidden email]> wrote:
> it doesn't actually ```import``` 1000+ es-modules inside the rollup-file. it just creates one es-module that exports a dictionary -- and assigns the dictionary 1000+ vanilla json-objects and functions.

The code provides a means to fetch N resources and export those resources within a single object.

> currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
> in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.
>
> if we're actually committed to native es-modules, then we either
> 1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
> 2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

You still have not clearly defined what you mean by "rolled-up". That language appears to be a random nickname, not any immutable principle that individuals are bound to recognize or observe (even if "rolled-up" were some form of a coding style or standard).

Nor is it clear what you mean by "production". 

There is no external central committee that stamps code as "production". Even if there were no individual is obliged to submit to such a procedure nor have any concern for such an arbitrary and irrelevant presumptive review of code. 

The only observable points are input and output. In general, how output is achieved is immaterial. If there are specific restrictions as to how the output can be achieved then those restrictions need to be clearly defined. 



The original post asked "how many async-modules can js-app practically load?" and mentioned "circular-references" (the thread appears to mainly be about one or more coding styles, not code itself) though as yet no code has been posted which demonstrates "circular-references" or any other coding problem.

On Sun, Jun 2, 2019 at 1:30 AM kai zhu <[hidden email]> wrote:
i played around with your code in jsfiddle [1], and understand it a little more.
it doesn't actually ```import``` 1000+ es-modules inside the rollup-file.
it just creates one es-module that exports a dictionary
 -- and assigns the dictionary 1000+ vanilla json-objects and functions.

```js
// the "rollup-file" is a single es-module
// that exports 1000+ vanilla dictionary-entries
const modules = {};

// this is not a es-module, nor is it rolled-up (external fetch)
modules.image = <await fetch json from gist.github.com>

// this is not a [rolled-up] es-module
modules.fn = function () {...}

// these are not [rolled-up] es-modules
Object.assign(modules, <1000 json-entries>)

export {modules}
```

currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.

if we're actually committed to native es-modules, then we either
1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

```js
// rollup.js with [hypothetical] # delimited es-modules
# module aa
import {bb} as bb;
export ...;

# module bb
export ...;
```

i'm generally skeptical of option 1, given how poorly npmjs.com has handled similar problems deduplicating children in node_modules/ directory.

[1] jsfiddle pseudo-module rollup

On Sat, Jun 1, 2019 at 5:30 PM guest271314 <[hidden email]> wrote:
> your rollup solution is interesting, 

What  is "rollup" referring to? 

> but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  

The duplicate ("collision") entry an ```try..catch``` block is included in the code to demonstrate given an array of module names to be exported and imported as identifiers 1) duplicate entries can be filtered; 2) if a plain object is exported duplicate identifiers ("collision") is not possible as a JavaScript plain object does not have duplicate property names ("collision"); if there is an issue with identifiers in a module the cause would not be the number of async-modules loaded ("how many"), but the naming of the identifiers within the code, using or not using ```const``` or ```let```. Still not sure what the actual issue is?

> don't completely understand how it works, 

Use an ```async``` function to fetch data, check for the described "collision" , create a ```data URI``` to be imported, optionally, append addition code to be executed within the ```<script type="module">```.

> but not sure of suitability for production-use, because of its dynamic <script> tag generation.

What is the issue with dynamic ```<script>``` tag generation? 

There is more than one possible approach to achieve the presumptive requirement, that is still not clear to the exclusion of what is not the expected result.

There were no restrictions described at the OP and following messages other than other than 

pure-es6 application with 20 es-modules rolled-up into one [production] bundle?

The example code uses only JavaScript implementation shipped with the browser without any external, third-party libraries.
 
What standard or definition are you relying for the meaning of the term "production-use"? What procedure are you using to determine if code is "production-use" "suitable"? How is that procedure related to "how many async-modules can js-app practically load?"?



On Sat, Jun 1, 2019 at 9:42 PM kai zhu <[hidden email]> wrote:
your rollup solution is interesting, but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  don't completely understand how it works, but not sure of suitability for production-use, because of its dynamic <script> tag generation.

```console
ReferenceError: module names ["yeqjqb02mvg3yze26rc5"] are not unique
    at data:application/javascript,%0A%20%20%20%20%20%20const%20modules...
```

On Sat, Jun 1, 2019 at 2:33 PM guest271314 <[hidden email]> wrote:
Re: how many async-modules can js-app practically load?

An example of exporting and importing loading 1000 properties in a single module, where duplicate property names are checked for. Since JavaScript plain objects cannot have duplicate property names there should not be any "collisions"; the code can check for and modify the object to be exported, though the last duplicate property name will be exported without any errors thrown unless the code is composed to throw such an error.

```
  (async() => {
    const oneThousandModules = encodeURIComponent(
      // substitute rand for a Set of module names to be exported
      // e.g. const moduleNames = ['moduleA', 'moduleB', ...moduleZ]
      `
      const modules = {};
      // set a function to be exported
      modules.fn = function() {return 'a function'};
      // function to set (1000) 'random' module names to be exported
      const rand = (seed = 'abcdefghijklmnopqrstuvwxyz0123456789', n = 5, len = seed.length) =>
        '.'.repeat(n).replace(/./g, _ => seed[~~(Math.random() * len)]);
        // use Set for unique module identifiers
        const moduleNames = [...Array(1000)].map(_ => rand());
        const moduleIdentifiers = new Set(moduleNames);
        // below line will cause ReferenceError to be thrown
        moduleNames.push(moduleNames[0]);
        try {
          if (moduleIdentifiers.size !== moduleNames.length) {
            // check for duplicates
            const duplicates = moduleNames.filter((moduleName, index) => moduleNames.indexOf(moduleName) !== index);
            // notification of duplicate module names
            throw new ReferenceError('module names ' + JSON.stringify(duplicates) + ' are not unique');
            // perform the designated task if duplicate module names are found here
          }
        } catch (e) {
          console.error(e);
          console.trace();
        }
        // get, set (sync or async) exported module here
        Object.assign(modules, ...[...moduleIdentifiers].map((id, value) => ({[id]:value})));
        // since JavaScript plain object cannot have duplicate property names
        // modules object will still be exported without duplicate property names
        // without collisions
        export {modules}
    `);
    const scriptText = `import {modules} from "data:application/javascript,${oneThousandModules};${encodeURIComponent('console.log(modules);for (const key in modules) {if (typeof modules[key] === \'function\') {console.log(modules[key]());}}')}"`;
    const script = document.createElement("script");
    script.type = "module";
    script.textContent = scriptText;
    document.head.appendChild(script);
  })();
```


On Sat, Jun 1, 2019 at 1:51 AM kai zhu <[hidden email]> wrote:
> Place all of the code to be exported in 1 file?  
 
that obviously will not work, because of module-scope collision.  can anyone share their experience on deploying a [babel-free] pure-es6 application with 20 es-modules rolled-up into one [production] bundle?  is it even possible?


On Fri, May 31, 2019 at 7:55 PM guest271314 <[hidden email]> wrote:
how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?

Place all of the code to be exported in 1 file? 

with some of them having circular-references

Not certain how that is possible when using ```import``` within ```<script type="module">```?

how many async-modules can js-app practically load?

Again, how many have you tried to load? 100? 500? 1000? Either should be possible.

What specific issue are you actually to resolve?

On Fri, May 31, 2019 at 5:40 PM kai zhu <[hidden email]> wrote:
> Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

was that with some combination of babel/rollup/webpack or pure-es6?
if i want to develop a pure-es6 webapp (no babel), how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?


On Fri, May 31, 2019 at 10:47 AM Isiah Meadows <[hidden email]> wrote:
If it's bundled by Rollup or Webpack into a single bundle, it's
equivalent to a single `<script type="module" src="...">` pointing
towards the original entry point, excluding network requests.* But in
either case, you aren't listing 50 scripts, you're only listing the
entry module and importing child modules within parent modules. Rollup
and Webpack do mostly the same thing browsers do when it comes to
resolving dependencies, just they generate a bundle afterwards where
browsers execute code afterwards. Also, it's worth noting that the gap
between a single large request and multiple smaller requests has
shrunk a lot since HTTP/2 came along, since it's binary, it allows
requests and response data to be interleaved, it better leverages the
underlying TCP protocol format, and it allows servers to send data
pre-emptively without the client requesting it first. (Web sockets are
built on this functionality.) It's still better to bundle in general,
but it's less of a problem not to.

This is *not* the case for `<script type="module">` elements - those
operate more like inline scripts that happen to have the ability to
`import`.

Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

* This is, of course, not the case if you are using pure ES6 and you
aren't using any plugins to, say, run the original source through
Babel for React + JSX or something.

-----

Isiah Meadows
[hidden email]
www.isiahmeadows.com
On Sat, May 25, 2019 at 2:12 AM kai zhu <[hidden email]> wrote:
>
> Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
>
> so async-loading 50 ```<script type="module">``` tags
> has equivalent side-effect
> as sync-loading single webpack-rollup (of same 50 modules)?
>
> i have nagging suspicion of doubts.  has anyone tried native async-loading large numbers (>10) of
> ```<script type="module">``` tags, and verify it resolves identically to using a single webpack-rollup?
>
> again, i'm not that knowledgeable on es-modules, so above question may be trivially true, and i'm just not aware.
>
> -kai
>
> On 24 May 2019, at 23:41, Isiah Meadows <[hidden email]> wrote:
>
> There's two main reasons why it scales:
>
> 1. Modules are strongly encapsulated while minimizing global pollution.
> 2. The resolution algorithm applies the same logic no matter how many
> modules are loaded.
>
> It's much easier for it to scale when you write the code unaware of
> how many modules you might be loading and unaware of how deep their
> dependency graph is. Fewer assumptions here is key. It's an
> engineering problem, but a relatively simple one.
>
> If you want a short example of how sync module resolution works, you
> can take a look at this little utility I wrote:
> https://github.com/isiahmeadows/simple-require-loader. That doesn't
> asynchronously resolve modules, but it should help explain the process
> from a synchronous standpoint. Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
> -----
>
> Isiah Meadows
> [hidden email]
> www.isiahmeadows.com
>
> On Thu, May 23, 2019 at 10:49 AM kai zhu <[hidden email]> wrote:
>
>
> actually, i admit i don't know what i'm talking about.  just generally confused (through ignorance) on how large-scale es-module dependencies resolve when loaded/imported asynchronously.
>
> On Wed, May 22, 2019 at 10:42 PM Logan Smyth <[hidden email]> wrote:
>
>
> Can you elaborate on what loading state you need to keep track of? What is the bottleneck that you run into? Also to be sure, when you say async-load, do you mean `import()`?
>
> On Wed, May 22, 2019, 20:17 kai zhu <[hidden email]> wrote:
>
>
> i don't use es-modules.
> but with amd/requirejs, I start having trouble with module-initializations in nodejs/browser at ~5 async modules (that may or may not have circular-references).  10 would be hard, and 20 would be near inhuman for me.
>
> can we say its somewhat impractical for most applications to load more than 50 async modules (with some of them having circular-references)?  and perhaps better design/spec module-loading mechanisms with this usability concern in mind?
>
> p.s. its also impractical for me to async-load 5 or more modules without using globalThis to keep track of each module's loading-state.
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
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Re: how many async-modules can js-app practically load?

guest271314
One option is to utilize ```shortName``` https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import#Import_an_export_with_a_more_convenient_alias

```
import {foo as foo1} from "./aa.js";
let bar1 = { baz: foo1 };
export { bar1 };

import {foo as foo2} from "./bb.js";
const bar2 = { baz: foo2 };
export { bar2 };
```

On Sun, Jun 2, 2019 at 11:05 PM kai zhu <[hidden email]> wrote:
not inline multiple ```export```'s, but inline multiple module-scopes.

```js
/*
 * how do you inline the two es-modules below
 * with colliding `foo` and `bar` variables?
 *
 * you can't unless you introduce new language-syntax
 * to somehow delimit their scopes
 */

// [hypothethical] es-module-scope delimiter
# es-module-scope "./inline.js"

// module ./inline.js
import { foo } from "./aa.js"
const bar = { baz: foo };
export { bar };



// [hypothethical] es-module-scope delimiter
# es-module-scope ./nextinline.js

// module ./nextinline.js
import { foo } from "./bb.js"
const bar = { baz: foo };  
export { bar };
```

On Sun, Jun 2, 2019 at 2:54 PM guest271314 <[hidden email]> wrote:
Multiple imports are already possible

```
import {inline} from "./inline.js";
import {nextInline} from "./nextInline.js";

const o = {
  a:1, b:2, c:3
};

// ...

export {o, cities, video, inline, nextInline};
```

Are you proposing multiple ```export```s?

```
export {o, cities, video, inline, nextInline};
o.c = 7;
export {o};
```



On Sun, Jun 2, 2019 at 6:19 PM kai zhu <[hidden email]> wrote:
[hidden email], your example again is not a [native] bundle of two or more inlined es-modules.  its just a single es-module that that fetches json data.

i'm asking if its desirable to inline multiple es-modules into a single file natively, e.g.:

```
/*
 * es-module.rollup.js
 * this [hypothetical] rollup-file contains multiple inlined es-modules
 * to improve load-performance in production-deployment.
 */

// 1. inlined es-module ./main.js
import { foo } from "./counter.js"
import { bar } from "./display.js"
foo(bar);

// 2. inlined es-module ./counter.js
var foo;
foo = function (bar) {
    bar();
};
export { foo }

// 3. inlined es-module ./display.js
var bar;
bar = function () {
    console.log("hello world");
};
export { bar }
```

this native es-module inline-capability may not be desirable to you, which is fine.  it would be a datapoint against this feature (and rely instead on pre-emptive import-maps and http2-push, as explained by @frederick and @isiah).


On Sun, Jun 2, 2019 at 11:22 AM guest271314 <[hidden email]> wrote:
1) original-question - is native es-module's async-behavior desirable?  async side-effects are difficult to manage -- i conjecture that async-loading 20 es-modules (with dependent side-effects) is not practical for most mortals to handle.

It depends on what you mean by "desirable" in a given context. 

There is no difference from loading 1 module and loading 1000 modules except for network cost, memory and disk space usage. 

Mortals can handle far more than loading 20 es-modules. 

What are the specific  "side-effects" that you are referring to?

describes the mechanism for how to hint the brower to pre-fetch 20 es-modules. but if you pre-fetch, then is loading-behavior effectively synchronous?

Resources can be "pre-fetched" using various means. From caching the first request and using the cached data instead of making future requests for the same resources to storing one or more entire directories in the browser configuration folder using `requestFileSystem` (Chromiom/Chrome).

but was unclear whether they were individual [async] ```<script type="module">``` tags, or some es5-transpiled rollup

There should not be any difference between the two approaches. If there is a difference then you should be able to clearly state what the difference is, and demonstrate the difference by reproduction, without speculating and not demonstrating a difference by means of reproduction.

2) the second-question about es-module rollups (which you and i are debating) stemmed from @isiah's response -- if he and everyone-else use es5-transpiled rollups (which i suspect), 

Do not care what "everyone-else" is supposedly doing. How can you possibly know what everyone-else is doing and even if you did know what third-parties are doing how does that affect what you are doing?

then shouldn't it be desirable for es-modules to natively support rollups as well?  currently, there's no way to natively rollup multiple es-modules into a single bundle.

There are ways to "bundle" multiple modules into a single export "natively", as demonstrated at the previously posted code.

Another example approach

```
// sync
const o = {
  a:1, b:2, c:3
};
// async
const cities = fetch("https://gist.githubusercontent.com/guest271314/ffac94353ab16f42160e/raw/aaee70a3e351f6c7bc00178eabb5970a02df87e9/states.json")
               .then(response => response.json())
               .catch(e => {console.error(e); return "error fetching cities module"});
// async            
const video = fetch("https://upload.wikimedia.org/wikipedia/commons/d/d9/120-cell.ogv")
               .then(response => response.blob())
              .catch(e => {console.error(e); return "error fetching video module"});
// multiple "modules" exported
export {o, cities, video};
```

at single ```<script type="module">```

```
    <script type="module">
      import * as o from "./script.js";
      (async(mods) => {
        for (const [key, value] of mods) {
          if (value instanceof Promise) {
            console.log("async module", key, await value)
          } else {
            console.log("sync module", key, value);
          }
        }
      })(Object.entries(o));
    </script>
```

Still there is no actual problem statement. Rather, there is conjecture without a definitive issue to solve. 
 

 

On Sun, Jun 2, 2019 at 3:54 AM kai zhu <[hidden email]> wrote:
i apologize for poor framing of my questions.  they are still formative, but i can clarify abit as follows:

1) original-question - is native es-module's async-behavior desirable?  async side-effects are difficult to manage -- i conjecture that async-loading 20 es-modules (with dependent side-effects) is not practical for most mortals to handle.
@frederick describes the mechanism for how to hint the brower to pre-fetch 20 es-modules. but if you pre-fetch, then is loading-behavior effectively synchronous?
@isiah says he has experience loading 50-100 modules, but was unclear whether they were individual [async] ```<script type="module">``` tags, or some es5-transpiled rollup.

i may be wrong about everything, as i'm a bit ignorant on what async actually means in es-modules (and appreciate it, if someone can clarify that).



2) the second-question about es-module rollups (which you and i are debating) stemmed from @isiah's response -- if he and everyone-else use es5-transpiled rollups (which i suspect), then shouldn't it be desirable for es-modules to natively support rollups as well?  currently, there's no way to natively rollup multiple es-modules into a single bundle.

this 2nd question also has implications about es-module's async-behavior (because rollups "load" modules in sync/blocking fashion).  this could change side-effect behaviors between development-mode (20 [async] ```<script type="module">``` tags) and production-mode (1 rollup-bundle).  again, i may be wrong about that, as i'm ignorant about what async actually is in es-modules.

-kai

On Sat, Jun 1, 2019 at 9:22 PM guest271314 <[hidden email]> wrote:
> it doesn't actually ```import``` 1000+ es-modules inside the rollup-file. it just creates one es-module that exports a dictionary -- and assigns the dictionary 1000+ vanilla json-objects and functions.

The code provides a means to fetch N resources and export those resources within a single object.

> currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
> in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.
>
> if we're actually committed to native es-modules, then we either
> 1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
> 2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

You still have not clearly defined what you mean by "rolled-up". That language appears to be a random nickname, not any immutable principle that individuals are bound to recognize or observe (even if "rolled-up" were some form of a coding style or standard).

Nor is it clear what you mean by "production". 

There is no external central committee that stamps code as "production". Even if there were no individual is obliged to submit to such a procedure nor have any concern for such an arbitrary and irrelevant presumptive review of code. 

The only observable points are input and output. In general, how output is achieved is immaterial. If there are specific restrictions as to how the output can be achieved then those restrictions need to be clearly defined. 



The original post asked "how many async-modules can js-app practically load?" and mentioned "circular-references" (the thread appears to mainly be about one or more coding styles, not code itself) though as yet no code has been posted which demonstrates "circular-references" or any other coding problem.

On Sun, Jun 2, 2019 at 1:30 AM kai zhu <[hidden email]> wrote:
i played around with your code in jsfiddle [1], and understand it a little more.
it doesn't actually ```import``` 1000+ es-modules inside the rollup-file.
it just creates one es-module that exports a dictionary
 -- and assigns the dictionary 1000+ vanilla json-objects and functions.

```js
// the "rollup-file" is a single es-module
// that exports 1000+ vanilla dictionary-entries
const modules = {};

// this is not a es-module, nor is it rolled-up (external fetch)
modules.image = <await fetch json from gist.github.com>

// this is not a [rolled-up] es-module
modules.fn = function () {...}

// these are not [rolled-up] es-modules
Object.assign(modules, <1000 json-entries>)

export {modules}
```

currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.

if we're actually committed to native es-modules, then we either
1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

```js
// rollup.js with [hypothetical] # delimited es-modules
# module aa
import {bb} as bb;
export ...;

# module bb
export ...;
```

i'm generally skeptical of option 1, given how poorly npmjs.com has handled similar problems deduplicating children in node_modules/ directory.

[1] jsfiddle pseudo-module rollup

On Sat, Jun 1, 2019 at 5:30 PM guest271314 <[hidden email]> wrote:
> your rollup solution is interesting, 

What  is "rollup" referring to? 

> but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  

The duplicate ("collision") entry an ```try..catch``` block is included in the code to demonstrate given an array of module names to be exported and imported as identifiers 1) duplicate entries can be filtered; 2) if a plain object is exported duplicate identifiers ("collision") is not possible as a JavaScript plain object does not have duplicate property names ("collision"); if there is an issue with identifiers in a module the cause would not be the number of async-modules loaded ("how many"), but the naming of the identifiers within the code, using or not using ```const``` or ```let```. Still not sure what the actual issue is?

> don't completely understand how it works, 

Use an ```async``` function to fetch data, check for the described "collision" , create a ```data URI``` to be imported, optionally, append addition code to be executed within the ```<script type="module">```.

> but not sure of suitability for production-use, because of its dynamic <script> tag generation.

What is the issue with dynamic ```<script>``` tag generation? 

There is more than one possible approach to achieve the presumptive requirement, that is still not clear to the exclusion of what is not the expected result.

There were no restrictions described at the OP and following messages other than other than 

pure-es6 application with 20 es-modules rolled-up into one [production] bundle?

The example code uses only JavaScript implementation shipped with the browser without any external, third-party libraries.
 
What standard or definition are you relying for the meaning of the term "production-use"? What procedure are you using to determine if code is "production-use" "suitable"? How is that procedure related to "how many async-modules can js-app practically load?"?



On Sat, Jun 1, 2019 at 9:42 PM kai zhu <[hidden email]> wrote:
your rollup solution is interesting, but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  don't completely understand how it works, but not sure of suitability for production-use, because of its dynamic <script> tag generation.

```console
ReferenceError: module names ["yeqjqb02mvg3yze26rc5"] are not unique
    at data:application/javascript,%0A%20%20%20%20%20%20const%20modules...
```

On Sat, Jun 1, 2019 at 2:33 PM guest271314 <[hidden email]> wrote:
Re: how many async-modules can js-app practically load?

An example of exporting and importing loading 1000 properties in a single module, where duplicate property names are checked for. Since JavaScript plain objects cannot have duplicate property names there should not be any "collisions"; the code can check for and modify the object to be exported, though the last duplicate property name will be exported without any errors thrown unless the code is composed to throw such an error.

```
  (async() => {
    const oneThousandModules = encodeURIComponent(
      // substitute rand for a Set of module names to be exported
      // e.g. const moduleNames = ['moduleA', 'moduleB', ...moduleZ]
      `
      const modules = {};
      // set a function to be exported
      modules.fn = function() {return 'a function'};
      // function to set (1000) 'random' module names to be exported
      const rand = (seed = 'abcdefghijklmnopqrstuvwxyz0123456789', n = 5, len = seed.length) =>
        '.'.repeat(n).replace(/./g, _ => seed[~~(Math.random() * len)]);
        // use Set for unique module identifiers
        const moduleNames = [...Array(1000)].map(_ => rand());
        const moduleIdentifiers = new Set(moduleNames);
        // below line will cause ReferenceError to be thrown
        moduleNames.push(moduleNames[0]);
        try {
          if (moduleIdentifiers.size !== moduleNames.length) {
            // check for duplicates
            const duplicates = moduleNames.filter((moduleName, index) => moduleNames.indexOf(moduleName) !== index);
            // notification of duplicate module names
            throw new ReferenceError('module names ' + JSON.stringify(duplicates) + ' are not unique');
            // perform the designated task if duplicate module names are found here
          }
        } catch (e) {
          console.error(e);
          console.trace();
        }
        // get, set (sync or async) exported module here
        Object.assign(modules, ...[...moduleIdentifiers].map((id, value) => ({[id]:value})));
        // since JavaScript plain object cannot have duplicate property names
        // modules object will still be exported without duplicate property names
        // without collisions
        export {modules}
    `);
    const scriptText = `import {modules} from "data:application/javascript,${oneThousandModules};${encodeURIComponent('console.log(modules);for (const key in modules) {if (typeof modules[key] === \'function\') {console.log(modules[key]());}}')}"`;
    const script = document.createElement("script");
    script.type = "module";
    script.textContent = scriptText;
    document.head.appendChild(script);
  })();
```


On Sat, Jun 1, 2019 at 1:51 AM kai zhu <[hidden email]> wrote:
> Place all of the code to be exported in 1 file?  
 
that obviously will not work, because of module-scope collision.  can anyone share their experience on deploying a [babel-free] pure-es6 application with 20 es-modules rolled-up into one [production] bundle?  is it even possible?


On Fri, May 31, 2019 at 7:55 PM guest271314 <[hidden email]> wrote:
how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?

Place all of the code to be exported in 1 file? 

with some of them having circular-references

Not certain how that is possible when using ```import``` within ```<script type="module">```?

how many async-modules can js-app practically load?

Again, how many have you tried to load? 100? 500? 1000? Either should be possible.

What specific issue are you actually to resolve?

On Fri, May 31, 2019 at 5:40 PM kai zhu <[hidden email]> wrote:
> Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

was that with some combination of babel/rollup/webpack or pure-es6?
if i want to develop a pure-es6 webapp (no babel), how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?


On Fri, May 31, 2019 at 10:47 AM Isiah Meadows <[hidden email]> wrote:
If it's bundled by Rollup or Webpack into a single bundle, it's
equivalent to a single `<script type="module" src="...">` pointing
towards the original entry point, excluding network requests.* But in
either case, you aren't listing 50 scripts, you're only listing the
entry module and importing child modules within parent modules. Rollup
and Webpack do mostly the same thing browsers do when it comes to
resolving dependencies, just they generate a bundle afterwards where
browsers execute code afterwards. Also, it's worth noting that the gap
between a single large request and multiple smaller requests has
shrunk a lot since HTTP/2 came along, since it's binary, it allows
requests and response data to be interleaved, it better leverages the
underlying TCP protocol format, and it allows servers to send data
pre-emptively without the client requesting it first. (Web sockets are
built on this functionality.) It's still better to bundle in general,
but it's less of a problem not to.

This is *not* the case for `<script type="module">` elements - those
operate more like inline scripts that happen to have the ability to
`import`.

Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

* This is, of course, not the case if you are using pure ES6 and you
aren't using any plugins to, say, run the original source through
Babel for React + JSX or something.

-----

Isiah Meadows
[hidden email]
www.isiahmeadows.com
On Sat, May 25, 2019 at 2:12 AM kai zhu <[hidden email]> wrote:
>
> Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
>
> so async-loading 50 ```<script type="module">``` tags
> has equivalent side-effect
> as sync-loading single webpack-rollup (of same 50 modules)?
>
> i have nagging suspicion of doubts.  has anyone tried native async-loading large numbers (>10) of
> ```<script type="module">``` tags, and verify it resolves identically to using a single webpack-rollup?
>
> again, i'm not that knowledgeable on es-modules, so above question may be trivially true, and i'm just not aware.
>
> -kai
>
> On 24 May 2019, at 23:41, Isiah Meadows <[hidden email]> wrote:
>
> There's two main reasons why it scales:
>
> 1. Modules are strongly encapsulated while minimizing global pollution.
> 2. The resolution algorithm applies the same logic no matter how many
> modules are loaded.
>
> It's much easier for it to scale when you write the code unaware of
> how many modules you might be loading and unaware of how deep their
> dependency graph is. Fewer assumptions here is key. It's an
> engineering problem, but a relatively simple one.
>
> If you want a short example of how sync module resolution works, you
> can take a look at this little utility I wrote:
> https://github.com/isiahmeadows/simple-require-loader. That doesn't
> asynchronously resolve modules, but it should help explain the process
> from a synchronous standpoint. Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
> -----
>
> Isiah Meadows
> [hidden email]
> www.isiahmeadows.com
>
> On Thu, May 23, 2019 at 10:49 AM kai zhu <[hidden email]> wrote:
>
>
> actually, i admit i don't know what i'm talking about.  just generally confused (through ignorance) on how large-scale es-module dependencies resolve when loaded/imported asynchronously.
>
> On Wed, May 22, 2019 at 10:42 PM Logan Smyth <[hidden email]> wrote:
>
>
> Can you elaborate on what loading state you need to keep track of? What is the bottleneck that you run into? Also to be sure, when you say async-load, do you mean `import()`?
>
> On Wed, May 22, 2019, 20:17 kai zhu <[hidden email]> wrote:
>
>
> i don't use es-modules.
> but with amd/requirejs, I start having trouble with module-initializations in nodejs/browser at ~5 async modules (that may or may not have circular-references).  10 would be hard, and 20 would be near inhuman for me.
>
> can we say its somewhat impractical for most applications to load more than 50 async modules (with some of them having circular-references)?  and perhaps better design/spec module-loading mechanisms with this usability concern in mind?
>
> p.s. its also impractical for me to async-load 5 or more modules without using globalThis to keep track of each module's loading-state.
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
_______________________________________________
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Re: how many async-modules can js-app practically load?

kai zhu
but that requires coordination among modules, which is not always possible.  the idea is to inline/rollup es-modules that may not have come from same developers (and whom are unaware their es-modules collide w/ others when rolled-up).

you should be able to natively transition from development-env (individual es-modules) -> production-env (rolled-up es-modules), w/o down-transpiling to es5-amdjs.



On Sun, Jun 2, 2019 at 8:29 PM guest271314 <[hidden email]> wrote:
One option is to utilize ```shortName``` https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import#Import_an_export_with_a_more_convenient_alias

```
import {foo as foo1} from "./aa.js";
let bar1 = { baz: foo1 };
export { bar1 };

import {foo as foo2} from "./bb.js";
const bar2 = { baz: foo2 };
export { bar2 };
```

On Sun, Jun 2, 2019 at 11:05 PM kai zhu <[hidden email]> wrote:
not inline multiple ```export```'s, but inline multiple module-scopes.

```js
/*
 * how do you inline the two es-modules below
 * with colliding `foo` and `bar` variables?
 *
 * you can't unless you introduce new language-syntax
 * to somehow delimit their scopes
 */

// [hypothethical] es-module-scope delimiter
# es-module-scope "./inline.js"

// module ./inline.js
import { foo } from "./aa.js"
const bar = { baz: foo };
export { bar };



// [hypothethical] es-module-scope delimiter
# es-module-scope ./nextinline.js

// module ./nextinline.js
import { foo } from "./bb.js"
const bar = { baz: foo };  
export { bar };
```

On Sun, Jun 2, 2019 at 2:54 PM guest271314 <[hidden email]> wrote:
Multiple imports are already possible

```
import {inline} from "./inline.js";
import {nextInline} from "./nextInline.js";

const o = {
  a:1, b:2, c:3
};

// ...

export {o, cities, video, inline, nextInline};
```

Are you proposing multiple ```export```s?

```
export {o, cities, video, inline, nextInline};
o.c = 7;
export {o};
```



On Sun, Jun 2, 2019 at 6:19 PM kai zhu <[hidden email]> wrote:
[hidden email], your example again is not a [native] bundle of two or more inlined es-modules.  its just a single es-module that that fetches json data.

i'm asking if its desirable to inline multiple es-modules into a single file natively, e.g.:

```
/*
 * es-module.rollup.js
 * this [hypothetical] rollup-file contains multiple inlined es-modules
 * to improve load-performance in production-deployment.
 */

// 1. inlined es-module ./main.js
import { foo } from "./counter.js"
import { bar } from "./display.js"
foo(bar);

// 2. inlined es-module ./counter.js
var foo;
foo = function (bar) {
    bar();
};
export { foo }

// 3. inlined es-module ./display.js
var bar;
bar = function () {
    console.log("hello world");
};
export { bar }
```

this native es-module inline-capability may not be desirable to you, which is fine.  it would be a datapoint against this feature (and rely instead on pre-emptive import-maps and http2-push, as explained by @frederick and @isiah).


On Sun, Jun 2, 2019 at 11:22 AM guest271314 <[hidden email]> wrote:
1) original-question - is native es-module's async-behavior desirable?  async side-effects are difficult to manage -- i conjecture that async-loading 20 es-modules (with dependent side-effects) is not practical for most mortals to handle.

It depends on what you mean by "desirable" in a given context. 

There is no difference from loading 1 module and loading 1000 modules except for network cost, memory and disk space usage. 

Mortals can handle far more than loading 20 es-modules. 

What are the specific  "side-effects" that you are referring to?

describes the mechanism for how to hint the brower to pre-fetch 20 es-modules. but if you pre-fetch, then is loading-behavior effectively synchronous?

Resources can be "pre-fetched" using various means. From caching the first request and using the cached data instead of making future requests for the same resources to storing one or more entire directories in the browser configuration folder using `requestFileSystem` (Chromiom/Chrome).

but was unclear whether they were individual [async] ```<script type="module">``` tags, or some es5-transpiled rollup

There should not be any difference between the two approaches. If there is a difference then you should be able to clearly state what the difference is, and demonstrate the difference by reproduction, without speculating and not demonstrating a difference by means of reproduction.

2) the second-question about es-module rollups (which you and i are debating) stemmed from @isiah's response -- if he and everyone-else use es5-transpiled rollups (which i suspect), 

Do not care what "everyone-else" is supposedly doing. How can you possibly know what everyone-else is doing and even if you did know what third-parties are doing how does that affect what you are doing?

then shouldn't it be desirable for es-modules to natively support rollups as well?  currently, there's no way to natively rollup multiple es-modules into a single bundle.

There are ways to "bundle" multiple modules into a single export "natively", as demonstrated at the previously posted code.

Another example approach

```
// sync
const o = {
  a:1, b:2, c:3
};
// async
const cities = fetch("https://gist.githubusercontent.com/guest271314/ffac94353ab16f42160e/raw/aaee70a3e351f6c7bc00178eabb5970a02df87e9/states.json")
               .then(response => response.json())
               .catch(e => {console.error(e); return "error fetching cities module"});
// async            
const video = fetch("https://upload.wikimedia.org/wikipedia/commons/d/d9/120-cell.ogv")
               .then(response => response.blob())
              .catch(e => {console.error(e); return "error fetching video module"});
// multiple "modules" exported
export {o, cities, video};
```

at single ```<script type="module">```

```
    <script type="module">
      import * as o from "./script.js";
      (async(mods) => {
        for (const [key, value] of mods) {
          if (value instanceof Promise) {
            console.log("async module", key, await value)
          } else {
            console.log("sync module", key, value);
          }
        }
      })(Object.entries(o));
    </script>
```

Still there is no actual problem statement. Rather, there is conjecture without a definitive issue to solve. 
 

 

On Sun, Jun 2, 2019 at 3:54 AM kai zhu <[hidden email]> wrote:
i apologize for poor framing of my questions.  they are still formative, but i can clarify abit as follows:

1) original-question - is native es-module's async-behavior desirable?  async side-effects are difficult to manage -- i conjecture that async-loading 20 es-modules (with dependent side-effects) is not practical for most mortals to handle.
@frederick describes the mechanism for how to hint the brower to pre-fetch 20 es-modules. but if you pre-fetch, then is loading-behavior effectively synchronous?
@isiah says he has experience loading 50-100 modules, but was unclear whether they were individual [async] ```<script type="module">``` tags, or some es5-transpiled rollup.

i may be wrong about everything, as i'm a bit ignorant on what async actually means in es-modules (and appreciate it, if someone can clarify that).



2) the second-question about es-module rollups (which you and i are debating) stemmed from @isiah's response -- if he and everyone-else use es5-transpiled rollups (which i suspect), then shouldn't it be desirable for es-modules to natively support rollups as well?  currently, there's no way to natively rollup multiple es-modules into a single bundle.

this 2nd question also has implications about es-module's async-behavior (because rollups "load" modules in sync/blocking fashion).  this could change side-effect behaviors between development-mode (20 [async] ```<script type="module">``` tags) and production-mode (1 rollup-bundle).  again, i may be wrong about that, as i'm ignorant about what async actually is in es-modules.

-kai

On Sat, Jun 1, 2019 at 9:22 PM guest271314 <[hidden email]> wrote:
> it doesn't actually ```import``` 1000+ es-modules inside the rollup-file. it just creates one es-module that exports a dictionary -- and assigns the dictionary 1000+ vanilla json-objects and functions.

The code provides a means to fetch N resources and export those resources within a single object.

> currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
> in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.
>
> if we're actually committed to native es-modules, then we either
> 1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
> 2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

You still have not clearly defined what you mean by "rolled-up". That language appears to be a random nickname, not any immutable principle that individuals are bound to recognize or observe (even if "rolled-up" were some form of a coding style or standard).

Nor is it clear what you mean by "production". 

There is no external central committee that stamps code as "production". Even if there were no individual is obliged to submit to such a procedure nor have any concern for such an arbitrary and irrelevant presumptive review of code. 

The only observable points are input and output. In general, how output is achieved is immaterial. If there are specific restrictions as to how the output can be achieved then those restrictions need to be clearly defined. 



The original post asked "how many async-modules can js-app practically load?" and mentioned "circular-references" (the thread appears to mainly be about one or more coding styles, not code itself) though as yet no code has been posted which demonstrates "circular-references" or any other coding problem.

On Sun, Jun 2, 2019 at 1:30 AM kai zhu <[hidden email]> wrote:
i played around with your code in jsfiddle [1], and understand it a little more.
it doesn't actually ```import``` 1000+ es-modules inside the rollup-file.
it just creates one es-module that exports a dictionary
 -- and assigns the dictionary 1000+ vanilla json-objects and functions.

```js
// the "rollup-file" is a single es-module
// that exports 1000+ vanilla dictionary-entries
const modules = {};

// this is not a es-module, nor is it rolled-up (external fetch)
modules.image = <await fetch json from gist.github.com>

// this is not a [rolled-up] es-module
modules.fn = function () {...}

// these are not [rolled-up] es-modules
Object.assign(modules, <1000 json-entries>)

export {modules}
```

currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.

if we're actually committed to native es-modules, then we either
1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

```js
// rollup.js with [hypothetical] # delimited es-modules
# module aa
import {bb} as bb;
export ...;

# module bb
export ...;
```

i'm generally skeptical of option 1, given how poorly npmjs.com has handled similar problems deduplicating children in node_modules/ directory.

[1] jsfiddle pseudo-module rollup

On Sat, Jun 1, 2019 at 5:30 PM guest271314 <[hidden email]> wrote:
> your rollup solution is interesting, 

What  is "rollup" referring to? 

> but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  

The duplicate ("collision") entry an ```try..catch``` block is included in the code to demonstrate given an array of module names to be exported and imported as identifiers 1) duplicate entries can be filtered; 2) if a plain object is exported duplicate identifiers ("collision") is not possible as a JavaScript plain object does not have duplicate property names ("collision"); if there is an issue with identifiers in a module the cause would not be the number of async-modules loaded ("how many"), but the naming of the identifiers within the code, using or not using ```const``` or ```let```. Still not sure what the actual issue is?

> don't completely understand how it works, 

Use an ```async``` function to fetch data, check for the described "collision" , create a ```data URI``` to be imported, optionally, append addition code to be executed within the ```<script type="module">```.

> but not sure of suitability for production-use, because of its dynamic <script> tag generation.

What is the issue with dynamic ```<script>``` tag generation? 

There is more than one possible approach to achieve the presumptive requirement, that is still not clear to the exclusion of what is not the expected result.

There were no restrictions described at the OP and following messages other than other than 

pure-es6 application with 20 es-modules rolled-up into one [production] bundle?

The example code uses only JavaScript implementation shipped with the browser without any external, third-party libraries.
 
What standard or definition are you relying for the meaning of the term "production-use"? What procedure are you using to determine if code is "production-use" "suitable"? How is that procedure related to "how many async-modules can js-app practically load?"?



On Sat, Jun 1, 2019 at 9:42 PM kai zhu <[hidden email]> wrote:
your rollup solution is interesting, but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  don't completely understand how it works, but not sure of suitability for production-use, because of its dynamic <script> tag generation.

```console
ReferenceError: module names ["yeqjqb02mvg3yze26rc5"] are not unique
    at data:application/javascript,%0A%20%20%20%20%20%20const%20modules...
```

On Sat, Jun 1, 2019 at 2:33 PM guest271314 <[hidden email]> wrote:
Re: how many async-modules can js-app practically load?

An example of exporting and importing loading 1000 properties in a single module, where duplicate property names are checked for. Since JavaScript plain objects cannot have duplicate property names there should not be any "collisions"; the code can check for and modify the object to be exported, though the last duplicate property name will be exported without any errors thrown unless the code is composed to throw such an error.

```
  (async() => {
    const oneThousandModules = encodeURIComponent(
      // substitute rand for a Set of module names to be exported
      // e.g. const moduleNames = ['moduleA', 'moduleB', ...moduleZ]
      `
      const modules = {};
      // set a function to be exported
      modules.fn = function() {return 'a function'};
      // function to set (1000) 'random' module names to be exported
      const rand = (seed = 'abcdefghijklmnopqrstuvwxyz0123456789', n = 5, len = seed.length) =>
        '.'.repeat(n).replace(/./g, _ => seed[~~(Math.random() * len)]);
        // use Set for unique module identifiers
        const moduleNames = [...Array(1000)].map(_ => rand());
        const moduleIdentifiers = new Set(moduleNames);
        // below line will cause ReferenceError to be thrown
        moduleNames.push(moduleNames[0]);
        try {
          if (moduleIdentifiers.size !== moduleNames.length) {
            // check for duplicates
            const duplicates = moduleNames.filter((moduleName, index) => moduleNames.indexOf(moduleName) !== index);
            // notification of duplicate module names
            throw new ReferenceError('module names ' + JSON.stringify(duplicates) + ' are not unique');
            // perform the designated task if duplicate module names are found here
          }
        } catch (e) {
          console.error(e);
          console.trace();
        }
        // get, set (sync or async) exported module here
        Object.assign(modules, ...[...moduleIdentifiers].map((id, value) => ({[id]:value})));
        // since JavaScript plain object cannot have duplicate property names
        // modules object will still be exported without duplicate property names
        // without collisions
        export {modules}
    `);
    const scriptText = `import {modules} from "data:application/javascript,${oneThousandModules};${encodeURIComponent('console.log(modules);for (const key in modules) {if (typeof modules[key] === \'function\') {console.log(modules[key]());}}')}"`;
    const script = document.createElement("script");
    script.type = "module";
    script.textContent = scriptText;
    document.head.appendChild(script);
  })();
```


On Sat, Jun 1, 2019 at 1:51 AM kai zhu <[hidden email]> wrote:
> Place all of the code to be exported in 1 file?  
 
that obviously will not work, because of module-scope collision.  can anyone share their experience on deploying a [babel-free] pure-es6 application with 20 es-modules rolled-up into one [production] bundle?  is it even possible?


On Fri, May 31, 2019 at 7:55 PM guest271314 <[hidden email]> wrote:
how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?

Place all of the code to be exported in 1 file? 

with some of them having circular-references

Not certain how that is possible when using ```import``` within ```<script type="module">```?

how many async-modules can js-app practically load?

Again, how many have you tried to load? 100? 500? 1000? Either should be possible.

What specific issue are you actually to resolve?

On Fri, May 31, 2019 at 5:40 PM kai zhu <[hidden email]> wrote:
> Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

was that with some combination of babel/rollup/webpack or pure-es6?
if i want to develop a pure-es6 webapp (no babel), how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?


On Fri, May 31, 2019 at 10:47 AM Isiah Meadows <[hidden email]> wrote:
If it's bundled by Rollup or Webpack into a single bundle, it's
equivalent to a single `<script type="module" src="...">` pointing
towards the original entry point, excluding network requests.* But in
either case, you aren't listing 50 scripts, you're only listing the
entry module and importing child modules within parent modules. Rollup
and Webpack do mostly the same thing browsers do when it comes to
resolving dependencies, just they generate a bundle afterwards where
browsers execute code afterwards. Also, it's worth noting that the gap
between a single large request and multiple smaller requests has
shrunk a lot since HTTP/2 came along, since it's binary, it allows
requests and response data to be interleaved, it better leverages the
underlying TCP protocol format, and it allows servers to send data
pre-emptively without the client requesting it first. (Web sockets are
built on this functionality.) It's still better to bundle in general,
but it's less of a problem not to.

This is *not* the case for `<script type="module">` elements - those
operate more like inline scripts that happen to have the ability to
`import`.

Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

* This is, of course, not the case if you are using pure ES6 and you
aren't using any plugins to, say, run the original source through
Babel for React + JSX or something.

-----

Isiah Meadows
[hidden email]
www.isiahmeadows.com
On Sat, May 25, 2019 at 2:12 AM kai zhu <[hidden email]> wrote:
>
> Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
>
> so async-loading 50 ```<script type="module">``` tags
> has equivalent side-effect
> as sync-loading single webpack-rollup (of same 50 modules)?
>
> i have nagging suspicion of doubts.  has anyone tried native async-loading large numbers (>10) of
> ```<script type="module">``` tags, and verify it resolves identically to using a single webpack-rollup?
>
> again, i'm not that knowledgeable on es-modules, so above question may be trivially true, and i'm just not aware.
>
> -kai
>
> On 24 May 2019, at 23:41, Isiah Meadows <[hidden email]> wrote:
>
> There's two main reasons why it scales:
>
> 1. Modules are strongly encapsulated while minimizing global pollution.
> 2. The resolution algorithm applies the same logic no matter how many
> modules are loaded.
>
> It's much easier for it to scale when you write the code unaware of
> how many modules you might be loading and unaware of how deep their
> dependency graph is. Fewer assumptions here is key. It's an
> engineering problem, but a relatively simple one.
>
> If you want a short example of how sync module resolution works, you
> can take a look at this little utility I wrote:
> https://github.com/isiahmeadows/simple-require-loader. That doesn't
> asynchronously resolve modules, but it should help explain the process
> from a synchronous standpoint. Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
> -----
>
> Isiah Meadows
> [hidden email]
> www.isiahmeadows.com
>
> On Thu, May 23, 2019 at 10:49 AM kai zhu <[hidden email]> wrote:
>
>
> actually, i admit i don't know what i'm talking about.  just generally confused (through ignorance) on how large-scale es-module dependencies resolve when loaded/imported asynchronously.
>
> On Wed, May 22, 2019 at 10:42 PM Logan Smyth <[hidden email]> wrote:
>
>
> Can you elaborate on what loading state you need to keep track of? What is the bottleneck that you run into? Also to be sure, when you say async-load, do you mean `import()`?
>
> On Wed, May 22, 2019, 20:17 kai zhu <[hidden email]> wrote:
>
>
> i don't use es-modules.
> but with amd/requirejs, I start having trouble with module-initializations in nodejs/browser at ~5 async modules (that may or may not have circular-references).  10 would be hard, and 20 would be near inhuman for me.
>
> can we say its somewhat impractical for most applications to load more than 50 async modules (with some of them having circular-references)?  and perhaps better design/spec module-loading mechanisms with this usability concern in mind?
>
> p.s. its also impractical for me to async-load 5 or more modules without using globalThis to keep track of each module's loading-state.
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
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Re: how many async-modules can js-app practically load?

guest271314
> but that requires coordination among modules, which is not always possible.  the idea is to inline/rollup es-modules that may not have come from same developers (and whom are unaware their es-modules collide w/ others when rolled-up).

How do you intend to know the names of the identifiers to import without "coordination" and check for duplicate identifier names and duplicate exports? 

On Mon, Jun 3, 2019 at 2:12 AM kai zhu <[hidden email]> wrote:
but that requires coordination among modules, which is not always possible.  the idea is to inline/rollup es-modules that may not have come from same developers (and whom are unaware their es-modules collide w/ others when rolled-up).

you should be able to natively transition from development-env (individual es-modules) -> production-env (rolled-up es-modules), w/o down-transpiling to es5-amdjs.



On Sun, Jun 2, 2019 at 8:29 PM guest271314 <[hidden email]> wrote:
One option is to utilize ```shortName``` https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import#Import_an_export_with_a_more_convenient_alias

```
import {foo as foo1} from "./aa.js";
let bar1 = { baz: foo1 };
export { bar1 };

import {foo as foo2} from "./bb.js";
const bar2 = { baz: foo2 };
export { bar2 };
```

On Sun, Jun 2, 2019 at 11:05 PM kai zhu <[hidden email]> wrote:
not inline multiple ```export```'s, but inline multiple module-scopes.

```js
/*
 * how do you inline the two es-modules below
 * with colliding `foo` and `bar` variables?
 *
 * you can't unless you introduce new language-syntax
 * to somehow delimit their scopes
 */

// [hypothethical] es-module-scope delimiter
# es-module-scope "./inline.js"

// module ./inline.js
import { foo } from "./aa.js"
const bar = { baz: foo };
export { bar };



// [hypothethical] es-module-scope delimiter
# es-module-scope ./nextinline.js

// module ./nextinline.js
import { foo } from "./bb.js"
const bar = { baz: foo };  
export { bar };
```

On Sun, Jun 2, 2019 at 2:54 PM guest271314 <[hidden email]> wrote:
Multiple imports are already possible

```
import {inline} from "./inline.js";
import {nextInline} from "./nextInline.js";

const o = {
  a:1, b:2, c:3
};

// ...

export {o, cities, video, inline, nextInline};
```

Are you proposing multiple ```export```s?

```
export {o, cities, video, inline, nextInline};
o.c = 7;
export {o};
```



On Sun, Jun 2, 2019 at 6:19 PM kai zhu <[hidden email]> wrote:
[hidden email], your example again is not a [native] bundle of two or more inlined es-modules.  its just a single es-module that that fetches json data.

i'm asking if its desirable to inline multiple es-modules into a single file natively, e.g.:

```
/*
 * es-module.rollup.js
 * this [hypothetical] rollup-file contains multiple inlined es-modules
 * to improve load-performance in production-deployment.
 */

// 1. inlined es-module ./main.js
import { foo } from "./counter.js"
import { bar } from "./display.js"
foo(bar);

// 2. inlined es-module ./counter.js
var foo;
foo = function (bar) {
    bar();
};
export { foo }

// 3. inlined es-module ./display.js
var bar;
bar = function () {
    console.log("hello world");
};
export { bar }
```

this native es-module inline-capability may not be desirable to you, which is fine.  it would be a datapoint against this feature (and rely instead on pre-emptive import-maps and http2-push, as explained by @frederick and @isiah).


On Sun, Jun 2, 2019 at 11:22 AM guest271314 <[hidden email]> wrote:
1) original-question - is native es-module's async-behavior desirable?  async side-effects are difficult to manage -- i conjecture that async-loading 20 es-modules (with dependent side-effects) is not practical for most mortals to handle.

It depends on what you mean by "desirable" in a given context. 

There is no difference from loading 1 module and loading 1000 modules except for network cost, memory and disk space usage. 

Mortals can handle far more than loading 20 es-modules. 

What are the specific  "side-effects" that you are referring to?

describes the mechanism for how to hint the brower to pre-fetch 20 es-modules. but if you pre-fetch, then is loading-behavior effectively synchronous?

Resources can be "pre-fetched" using various means. From caching the first request and using the cached data instead of making future requests for the same resources to storing one or more entire directories in the browser configuration folder using `requestFileSystem` (Chromiom/Chrome).

but was unclear whether they were individual [async] ```<script type="module">``` tags, or some es5-transpiled rollup

There should not be any difference between the two approaches. If there is a difference then you should be able to clearly state what the difference is, and demonstrate the difference by reproduction, without speculating and not demonstrating a difference by means of reproduction.

2) the second-question about es-module rollups (which you and i are debating) stemmed from @isiah's response -- if he and everyone-else use es5-transpiled rollups (which i suspect), 

Do not care what "everyone-else" is supposedly doing. How can you possibly know what everyone-else is doing and even if you did know what third-parties are doing how does that affect what you are doing?

then shouldn't it be desirable for es-modules to natively support rollups as well?  currently, there's no way to natively rollup multiple es-modules into a single bundle.

There are ways to "bundle" multiple modules into a single export "natively", as demonstrated at the previously posted code.

Another example approach

```
// sync
const o = {
  a:1, b:2, c:3
};
// async
const cities = fetch("https://gist.githubusercontent.com/guest271314/ffac94353ab16f42160e/raw/aaee70a3e351f6c7bc00178eabb5970a02df87e9/states.json")
               .then(response => response.json())
               .catch(e => {console.error(e); return "error fetching cities module"});
// async            
const video = fetch("https://upload.wikimedia.org/wikipedia/commons/d/d9/120-cell.ogv")
               .then(response => response.blob())
              .catch(e => {console.error(e); return "error fetching video module"});
// multiple "modules" exported
export {o, cities, video};
```

at single ```<script type="module">```

```
    <script type="module">
      import * as o from "./script.js";
      (async(mods) => {
        for (const [key, value] of mods) {
          if (value instanceof Promise) {
            console.log("async module", key, await value)
          } else {
            console.log("sync module", key, value);
          }
        }
      })(Object.entries(o));
    </script>
```

Still there is no actual problem statement. Rather, there is conjecture without a definitive issue to solve. 
 

 

On Sun, Jun 2, 2019 at 3:54 AM kai zhu <[hidden email]> wrote:
i apologize for poor framing of my questions.  they are still formative, but i can clarify abit as follows:

1) original-question - is native es-module's async-behavior desirable?  async side-effects are difficult to manage -- i conjecture that async-loading 20 es-modules (with dependent side-effects) is not practical for most mortals to handle.
@frederick describes the mechanism for how to hint the brower to pre-fetch 20 es-modules. but if you pre-fetch, then is loading-behavior effectively synchronous?
@isiah says he has experience loading 50-100 modules, but was unclear whether they were individual [async] ```<script type="module">``` tags, or some es5-transpiled rollup.

i may be wrong about everything, as i'm a bit ignorant on what async actually means in es-modules (and appreciate it, if someone can clarify that).



2) the second-question about es-module rollups (which you and i are debating) stemmed from @isiah's response -- if he and everyone-else use es5-transpiled rollups (which i suspect), then shouldn't it be desirable for es-modules to natively support rollups as well?  currently, there's no way to natively rollup multiple es-modules into a single bundle.

this 2nd question also has implications about es-module's async-behavior (because rollups "load" modules in sync/blocking fashion).  this could change side-effect behaviors between development-mode (20 [async] ```<script type="module">``` tags) and production-mode (1 rollup-bundle).  again, i may be wrong about that, as i'm ignorant about what async actually is in es-modules.

-kai

On Sat, Jun 1, 2019 at 9:22 PM guest271314 <[hidden email]> wrote:
> it doesn't actually ```import``` 1000+ es-modules inside the rollup-file. it just creates one es-module that exports a dictionary -- and assigns the dictionary 1000+ vanilla json-objects and functions.

The code provides a means to fetch N resources and export those resources within a single object.

> currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
> in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.
>
> if we're actually committed to native es-modules, then we either
> 1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
> 2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

You still have not clearly defined what you mean by "rolled-up". That language appears to be a random nickname, not any immutable principle that individuals are bound to recognize or observe (even if "rolled-up" were some form of a coding style or standard).

Nor is it clear what you mean by "production". 

There is no external central committee that stamps code as "production". Even if there were no individual is obliged to submit to such a procedure nor have any concern for such an arbitrary and irrelevant presumptive review of code. 

The only observable points are input and output. In general, how output is achieved is immaterial. If there are specific restrictions as to how the output can be achieved then those restrictions need to be clearly defined. 



The original post asked "how many async-modules can js-app practically load?" and mentioned "circular-references" (the thread appears to mainly be about one or more coding styles, not code itself) though as yet no code has been posted which demonstrates "circular-references" or any other coding problem.

On Sun, Jun 2, 2019 at 1:30 AM kai zhu <[hidden email]> wrote:
i played around with your code in jsfiddle [1], and understand it a little more.
it doesn't actually ```import``` 1000+ es-modules inside the rollup-file.
it just creates one es-module that exports a dictionary
 -- and assigns the dictionary 1000+ vanilla json-objects and functions.

```js
// the "rollup-file" is a single es-module
// that exports 1000+ vanilla dictionary-entries
const modules = {};

// this is not a es-module, nor is it rolled-up (external fetch)
modules.image = <await fetch json from gist.github.com>

// this is not a [rolled-up] es-module
modules.fn = function () {...}

// these are not [rolled-up] es-modules
Object.assign(modules, <1000 json-entries>)

export {modules}
```

currently, as i'm aware, nobody uses native es-modules in production, because it cannot be rolled-up.
in practice es-modules are [babel] transpiled down to es5-amd (or similar) for rollup-purposes.

if we're actually committed to native es-modules, then we either
1) need to depend on embedders like [hidden email] to create sophisticated cache-systems, or
2) introduce new language-syntax to delimit es-modules for rollup-purposes, e.g.

```js
// rollup.js with [hypothetical] # delimited es-modules
# module aa
import {bb} as bb;
export ...;

# module bb
export ...;
```

i'm generally skeptical of option 1, given how poorly npmjs.com has handled similar problems deduplicating children in node_modules/ directory.

[1] jsfiddle pseudo-module rollup

On Sat, Jun 1, 2019 at 5:30 PM guest271314 <[hidden email]> wrote:
> your rollup solution is interesting, 

What  is "rollup" referring to? 

> but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  

The duplicate ("collision") entry an ```try..catch``` block is included in the code to demonstrate given an array of module names to be exported and imported as identifiers 1) duplicate entries can be filtered; 2) if a plain object is exported duplicate identifiers ("collision") is not possible as a JavaScript plain object does not have duplicate property names ("collision"); if there is an issue with identifiers in a module the cause would not be the number of async-modules loaded ("how many"), but the naming of the identifiers within the code, using or not using ```const``` or ```let```. Still not sure what the actual issue is?

> don't completely understand how it works, 

Use an ```async``` function to fetch data, check for the described "collision" , create a ```data URI``` to be imported, optionally, append addition code to be executed within the ```<script type="module">```.

> but not sure of suitability for production-use, because of its dynamic <script> tag generation.

What is the issue with dynamic ```<script>``` tag generation? 

There is more than one possible approach to achieve the presumptive requirement, that is still not clear to the exclusion of what is not the expected result.

There were no restrictions described at the OP and following messages other than other than 

pure-es6 application with 20 es-modules rolled-up into one [production] bundle?

The example code uses only JavaScript implementation shipped with the browser without any external, third-party libraries.
 
What standard or definition are you relying for the meaning of the term "production-use"? What procedure are you using to determine if code is "production-use" "suitable"? How is that procedure related to "how many async-modules can js-app practically load?"?



On Sat, Jun 1, 2019 at 9:42 PM kai zhu <[hidden email]> wrote:
your rollup solution is interesting, but i get an error when run in chrome (i changed to n=20 to prevent name-collision, but it still happens).  don't completely understand how it works, but not sure of suitability for production-use, because of its dynamic <script> tag generation.

```console
ReferenceError: module names ["yeqjqb02mvg3yze26rc5"] are not unique
    at data:application/javascript,%0A%20%20%20%20%20%20const%20modules...
```

On Sat, Jun 1, 2019 at 2:33 PM guest271314 <[hidden email]> wrote:
Re: how many async-modules can js-app practically load?

An example of exporting and importing loading 1000 properties in a single module, where duplicate property names are checked for. Since JavaScript plain objects cannot have duplicate property names there should not be any "collisions"; the code can check for and modify the object to be exported, though the last duplicate property name will be exported without any errors thrown unless the code is composed to throw such an error.

```
  (async() => {
    const oneThousandModules = encodeURIComponent(
      // substitute rand for a Set of module names to be exported
      // e.g. const moduleNames = ['moduleA', 'moduleB', ...moduleZ]
      `
      const modules = {};
      // set a function to be exported
      modules.fn = function() {return 'a function'};
      // function to set (1000) 'random' module names to be exported
      const rand = (seed = 'abcdefghijklmnopqrstuvwxyz0123456789', n = 5, len = seed.length) =>
        '.'.repeat(n).replace(/./g, _ => seed[~~(Math.random() * len)]);
        // use Set for unique module identifiers
        const moduleNames = [...Array(1000)].map(_ => rand());
        const moduleIdentifiers = new Set(moduleNames);
        // below line will cause ReferenceError to be thrown
        moduleNames.push(moduleNames[0]);
        try {
          if (moduleIdentifiers.size !== moduleNames.length) {
            // check for duplicates
            const duplicates = moduleNames.filter((moduleName, index) => moduleNames.indexOf(moduleName) !== index);
            // notification of duplicate module names
            throw new ReferenceError('module names ' + JSON.stringify(duplicates) + ' are not unique');
            // perform the designated task if duplicate module names are found here
          }
        } catch (e) {
          console.error(e);
          console.trace();
        }
        // get, set (sync or async) exported module here
        Object.assign(modules, ...[...moduleIdentifiers].map((id, value) => ({[id]:value})));
        // since JavaScript plain object cannot have duplicate property names
        // modules object will still be exported without duplicate property names
        // without collisions
        export {modules}
    `);
    const scriptText = `import {modules} from "data:application/javascript,${oneThousandModules};${encodeURIComponent('console.log(modules);for (const key in modules) {if (typeof modules[key] === \'function\') {console.log(modules[key]());}}')}"`;
    const script = document.createElement("script");
    script.type = "module";
    script.textContent = scriptText;
    document.head.appendChild(script);
  })();
```


On Sat, Jun 1, 2019 at 1:51 AM kai zhu <[hidden email]> wrote:
> Place all of the code to be exported in 1 file?  
 
that obviously will not work, because of module-scope collision.  can anyone share their experience on deploying a [babel-free] pure-es6 application with 20 es-modules rolled-up into one [production] bundle?  is it even possible?


On Fri, May 31, 2019 at 7:55 PM guest271314 <[hidden email]> wrote:
how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?

Place all of the code to be exported in 1 file? 

with some of them having circular-references

Not certain how that is possible when using ```import``` within ```<script type="module">```?

how many async-modules can js-app practically load?

Again, how many have you tried to load? 100? 500? 1000? Either should be possible.

What specific issue are you actually to resolve?

On Fri, May 31, 2019 at 5:40 PM kai zhu <[hidden email]> wrote:
> Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

was that with some combination of babel/rollup/webpack or pure-es6?
if i want to develop a pure-es6 webapp (no babel), how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?


On Fri, May 31, 2019 at 10:47 AM Isiah Meadows <[hidden email]> wrote:
If it's bundled by Rollup or Webpack into a single bundle, it's
equivalent to a single `<script type="module" src="...">` pointing
towards the original entry point, excluding network requests.* But in
either case, you aren't listing 50 scripts, you're only listing the
entry module and importing child modules within parent modules. Rollup
and Webpack do mostly the same thing browsers do when it comes to
resolving dependencies, just they generate a bundle afterwards where
browsers execute code afterwards. Also, it's worth noting that the gap
between a single large request and multiple smaller requests has
shrunk a lot since HTTP/2 came along, since it's binary, it allows
requests and response data to be interleaved, it better leverages the
underlying TCP protocol format, and it allows servers to send data
pre-emptively without the client requesting it first. (Web sockets are
built on this functionality.) It's still better to bundle in general,
but it's less of a problem not to.

This is *not* the case for `<script type="module">` elements - those
operate more like inline scripts that happen to have the ability to
`import`.

Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
modules is *easy* to achieve in single-page apps.

* This is, of course, not the case if you are using pure ES6 and you
aren't using any plugins to, say, run the original source through
Babel for React + JSX or something.

-----

Isiah Meadows
[hidden email]
www.isiahmeadows.com
On Sat, May 25, 2019 at 2:12 AM kai zhu <[hidden email]> wrote:
>
> Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
>
> so async-loading 50 ```<script type="module">``` tags
> has equivalent side-effect
> as sync-loading single webpack-rollup (of same 50 modules)?
>
> i have nagging suspicion of doubts.  has anyone tried native async-loading large numbers (>10) of
> ```<script type="module">``` tags, and verify it resolves identically to using a single webpack-rollup?
>
> again, i'm not that knowledgeable on es-modules, so above question may be trivially true, and i'm just not aware.
>
> -kai
>
> On 24 May 2019, at 23:41, Isiah Meadows <[hidden email]> wrote:
>
> There's two main reasons why it scales:
>
> 1. Modules are strongly encapsulated while minimizing global pollution.
> 2. The resolution algorithm applies the same logic no matter how many
> modules are loaded.
>
> It's much easier for it to scale when you write the code unaware of
> how many modules you might be loading and unaware of how deep their
> dependency graph is. Fewer assumptions here is key. It's an
> engineering problem, but a relatively simple one.
>
> If you want a short example of how sync module resolution works, you
> can take a look at this little utility I wrote:
> https://github.com/isiahmeadows/simple-require-loader. That doesn't
> asynchronously resolve modules, but it should help explain the process
> from a synchronous standpoint. Asynchronous loading differs only in
> that it takes more code to express the same logic and you have to take
> into account concurrent requests (and you need to cache the request,
> not the result), but it's otherwise the same from 1km away.
>
> -----
>
> Isiah Meadows
> [hidden email]
> www.isiahmeadows.com
>
> On Thu, May 23, 2019 at 10:49 AM kai zhu <[hidden email]> wrote:
>
>
> actually, i admit i don't know what i'm talking about.  just generally confused (through ignorance) on how large-scale es-module dependencies resolve when loaded/imported asynchronously.
>
> On Wed, May 22, 2019 at 10:42 PM Logan Smyth <[hidden email]> wrote:
>
>
> Can you elaborate on what loading state you need to keep track of? What is the bottleneck that you run into? Also to be sure, when you say async-load, do you mean `import()`?
>
> On Wed, May 22, 2019, 20:17 kai zhu <[hidden email]> wrote:
>
>
> i don't use es-modules.
> but with amd/requirejs, I start having trouble with module-initializations in nodejs/browser at ~5 async modules (that may or may not have circular-references).  10 would be hard, and 20 would be near inhuman for me.
>
> can we say its somewhat impractical for most applications to load more than 50 async modules (with some of them having circular-references)?  and perhaps better design/spec module-loading mechanisms with this usability concern in mind?
>
> p.s. its also impractical for me to async-load 5 or more modules without using globalThis to keep track of each module's loading-state.
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
> _______________________________________________
> es-discuss mailing list
> [hidden email]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
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Re: how many async-modules can js-app practically load?

kai zhu
you would need to introduce a new language-syntax that hints delimited module-scope, e.g.

```js
/*
 * es-module.rollup.js
 * 
 * example rolling-up es-modules with [hypothetical] pragma
 * "use module_scope xxx";
 * which would be web-compat and minifier-friendly
 */

"use module_scope ./aa.js";
// foo is scoped inside module_scope ./aa.js
var foo = ...
...

"use module_scope ./bb.js";
// foo is scoped inside module_scope ./bb.js
var foo = ...
...
```

i'll be honest.  i'm not really proposing this language-syntax in good-faith, as javascript is already chock-full of confusing-features that are distracting/harmful to UX-workflow programming.

i'm mainly criticizing tc39 for their design-decision pushing through es-modules, and how disruptive it is to operationalize (natively, w/o transpiling) in production-systems.  web-development could've stayed simpler if the committee had done absolutely nothing.  people would've continued using es5-style rollups (w/ yui/amdjs-like module-loaders), and devop-folks wouldn't be forced to deal with import-maps and http2-push to solve a problem that shouldn't have existed.



On Sun, Jun 2, 2019 at 9:25 PM guest271314 <[hidden email]> wrote:
> but that requires coordination among modules, which is not always possible.  the idea is to inline/rollup es-modules that may not have come from same developers (and whom are unaware their es-modules collide w/ others when rolled-up).

How do you intend to know the names of the identifiers to import without "coordination" and check for duplicate identifier names and duplicate exports? 

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Re: how many async-modules can js-app practically load?

guest271314
Thus far each of the prospective edge cases relevant to the proposal have been technically solved, save for duplicate identifier names and exports from the same file, which appears to be avoidable.

Have no "faith" in anything, therefore "good" and "bad" preceding "faith" are as irrelevant as "good" or "bad". 

You can use what is available now and write your own language in your spare time 
(What programming languages have been created by PPCG users? https://codegolf.meta.stackexchange.com/q/6918) though beware ("Anyone, from the most clueless amateur to the best cryptographer, can create an algorithm that he himself can't break." -Schneier, Bruce (1998-10-15). Memo to the Amateur Cipher Design. Cryptogram newsletter. (aka Schneier's Law)

On Mon, Jun 3, 2019 at 4:12 AM kai zhu <[hidden email]> wrote:
you would need to introduce a new language-syntax that hints delimited module-scope, e.g.

```js
/*
 * es-module.rollup.js
 * 
 * example rolling-up es-modules with [hypothetical] pragma
 * "use module_scope xxx";
 * which would be web-compat and minifier-friendly
 */

"use module_scope ./aa.js";
// foo is scoped inside module_scope ./aa.js
var foo = ...
...

"use module_scope ./bb.js";
// foo is scoped inside module_scope ./bb.js
var foo = ...
...
```

i'll be honest.  i'm not really proposing this language-syntax in good-faith, as javascript is already chock-full of confusing-features that are distracting/harmful to UX-workflow programming.

i'm mainly criticizing tc39 for their design-decision pushing through es-modules, and how disruptive it is to operationalize (natively, w/o transpiling) in production-systems.  web-development could've stayed simpler if the committee had done absolutely nothing.  people would've continued using es5-style rollups (w/ yui/amdjs-like module-loaders), and devop-folks wouldn't be forced to deal with import-maps and http2-push to solve a problem that shouldn't have existed.



On Sun, Jun 2, 2019 at 9:25 PM guest271314 <[hidden email]> wrote:
> but that requires coordination among modules, which is not always possible.  the idea is to inline/rollup es-modules that may not have come from same developers (and whom are unaware their es-modules collide w/ others when rolled-up).

How do you intend to know the names of the identifiers to import without "coordination" and check for duplicate identifier names and duplicate exports? 

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Re: how many async-modules can js-app practically load?

Isiah Meadows-2
In reply to this post by kai zhu
That would be pure ES6 running in Chrome natively, before I introduced
Webpack or Rollup to generate the bundle. Transitioning to those is as
simple as:

1. Installing the relevant build tool.
2. Creating the relevant config file.
3. Changing the HTML file to load the bundle instead of the entry point.

I generally use either a bundler in both dev + prod or just a bunch of
ES6 modules in dev + prod - I don't mix them, because it makes it
harder to maintain in the future. (Native for dev, Rollup for prod got
unwieldy within literally just the entry point. Having to switch
between entry points is itself enough to get in the way of things.)

-----

Isiah Meadows
[hidden email]
www.isiahmeadows.com

On Fri, May 31, 2019 at 1:40 PM kai zhu <[hidden email]> wrote:

>
> > Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
> modules is *easy* to achieve in single-page apps.
>
> was that with some combination of babel/rollup/webpack or pure-es6?
> if i want to develop a pure-es6 webapp (no babel), how would i transition from development-mode (20 es-module files) -> production-mode (1 rollup file)?
>
>
> On Fri, May 31, 2019 at 10:47 AM Isiah Meadows <[hidden email]> wrote:
>>
>> If it's bundled by Rollup or Webpack into a single bundle, it's
>> equivalent to a single `<script type="module" src="...">` pointing
>> towards the original entry point, excluding network requests.* But in
>> either case, you aren't listing 50 scripts, you're only listing the
>> entry module and importing child modules within parent modules. Rollup
>> and Webpack do mostly the same thing browsers do when it comes to
>> resolving dependencies, just they generate a bundle afterwards where
>> browsers execute code afterwards. Also, it's worth noting that the gap
>> between a single large request and multiple smaller requests has
>> shrunk a lot since HTTP/2 came along, since it's binary, it allows
>> requests and response data to be interleaved, it better leverages the
>> underlying TCP protocol format, and it allows servers to send data
>> pre-emptively without the client requesting it first. (Web sockets are
>> built on this functionality.) It's still better to bundle in general,
>> but it's less of a problem not to.
>>
>> This is *not* the case for `<script type="module">` elements - those
>> operate more like inline scripts that happen to have the ability to
>> `import`.
>>
>> Oh, and yes, I've loaded upwards of 50-100 modules in development. 20
>> modules is *easy* to achieve in single-page apps.
>>
>> * This is, of course, not the case if you are using pure ES6 and you
>> aren't using any plugins to, say, run the original source through
>> Babel for React + JSX or something.
>>
>> -----
>>
>> Isiah Meadows
>> [hidden email]
>> www.isiahmeadows.com
>> On Sat, May 25, 2019 at 2:12 AM kai zhu <[hidden email]> wrote:
>> >
>> > Asynchronous loading differs only in
>> > that it takes more code to express the same logic and you have to take
>> > into account concurrent requests (and you need to cache the request,
>> > not the result), but it's otherwise the same from 1km away.
>> >
>> >
>> > so async-loading 50 ```<script type="module">``` tags
>> > has equivalent side-effect
>> > as sync-loading single webpack-rollup (of same 50 modules)?
>> >
>> > i have nagging suspicion of doubts.  has anyone tried native async-loading large numbers (>10) of
>> > ```<script type="module">``` tags, and verify it resolves identically to using a single webpack-rollup?
>> >
>> > again, i'm not that knowledgeable on es-modules, so above question may be trivially true, and i'm just not aware.
>> >
>> > -kai
>> >
>> > On 24 May 2019, at 23:41, Isiah Meadows <[hidden email]> wrote:
>> >
>> > There's two main reasons why it scales:
>> >
>> > 1. Modules are strongly encapsulated while minimizing global pollution.
>> > 2. The resolution algorithm applies the same logic no matter how many
>> > modules are loaded.
>> >
>> > It's much easier for it to scale when you write the code unaware of
>> > how many modules you might be loading and unaware of how deep their
>> > dependency graph is. Fewer assumptions here is key. It's an
>> > engineering problem, but a relatively simple one.
>> >
>> > If you want a short example of how sync module resolution works, you
>> > can take a look at this little utility I wrote:
>> > https://github.com/isiahmeadows/simple-require-loader. That doesn't
>> > asynchronously resolve modules, but it should help explain the process
>> > from a synchronous standpoint. Asynchronous loading differs only in
>> > that it takes more code to express the same logic and you have to take
>> > into account concurrent requests (and you need to cache the request,
>> > not the result), but it's otherwise the same from 1km away.
>> >
>> > -----
>> >
>> > Isiah Meadows
>> > [hidden email]
>> > www.isiahmeadows.com
>> >
>> > On Thu, May 23, 2019 at 10:49 AM kai zhu <[hidden email]> wrote:
>> >
>> >
>> > actually, i admit i don't know what i'm talking about.  just generally confused (through ignorance) on how large-scale es-module dependencies resolve when loaded/imported asynchronously.
>> >
>> > On Wed, May 22, 2019 at 10:42 PM Logan Smyth <[hidden email]> wrote:
>> >
>> >
>> > Can you elaborate on what loading state you need to keep track of? What is the bottleneck that you run into? Also to be sure, when you say async-load, do you mean `import()`?
>> >
>> > On Wed, May 22, 2019, 20:17 kai zhu <[hidden email]> wrote:
>> >
>> >
>> > i don't use es-modules.
>> > but with amd/requirejs, I start having trouble with module-initializations in nodejs/browser at ~5 async modules (that may or may not have circular-references).  10 would be hard, and 20 would be near inhuman for me.
>> >
>> > can we say its somewhat impractical for most applications to load more than 50 async modules (with some of them having circular-references)?  and perhaps better design/spec module-loading mechanisms with this usability concern in mind?
>> >
>> > p.s. its also impractical for me to async-load 5 or more modules without using globalThis to keep track of each module's loading-state.
>> > _______________________________________________
>> > es-discuss mailing list
>> > [hidden email]
>> > https://mail.mozilla.org/listinfo/es-discuss
>> >
>> >
>> > _______________________________________________
>> > es-discuss mailing list
>> > [hidden email]
>> > https://mail.mozilla.org/listinfo/es-discuss
>> >
>> >
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