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

guest271314 guest271314 at gmail.com
Sun Jun 2 02:22:47 UTC 2019


> 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 loading-dev at chromium.org 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 <kaizhu256 at gmail.com> 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 loading-dev at chromium.org 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
> https://jsfiddle.net/06twrLfd/
>
> On Sat, Jun 1, 2019 at 5:30 PM guest271314 <guest271314 at gmail.com> 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 <kaizhu256 at gmail.com> 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 <guest271314 at gmail.com>
>>> 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);
>>>>   })();
>>>> ```
>>>>
>>>> plnkr https://plnkr.co/edit/CgEhBY?p=preview
>>>>
>>>> On Sat, Jun 1, 2019 at 1:51 AM kai zhu <kaizhu256 at gmail.com> 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 <guest271314 at gmail.com>
>>>>> 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 <kaizhu256 at gmail.com> 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 <
>>>>>>> isiahmeadows at gmail.com> 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
>>>>>>>> contact at isiahmeadows.com
>>>>>>>> www.isiahmeadows.com
>>>>>>>> On Sat, May 25, 2019 at 2:12 AM kai zhu <kaizhu256 at gmail.com>
>>>>>>>> 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 <isiahmeadows at gmail.com>
>>>>>>>> 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
>>>>>>>> > contact at isiahmeadows.com
>>>>>>>> > www.isiahmeadows.com
>>>>>>>> >
>>>>>>>> > On Thu, May 23, 2019 at 10:49 AM kai zhu <kaizhu256 at gmail.com>
>>>>>>>> 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 <
>>>>>>>> loganfsmyth at gmail.com> 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 <kaizhu256 at gmail.com> 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
>>>>>>>> > es-discuss at mozilla.org
>>>>>>>> > https://mail.mozilla.org/listinfo/es-discuss
>>>>>>>> >
>>>>>>>> >
>>>>>>>> > _______________________________________________
>>>>>>>> > es-discuss mailing list
>>>>>>>> > es-discuss at mozilla.org
>>>>>>>> > https://mail.mozilla.org/listinfo/es-discuss
>>>>>>>> >
>>>>>>>> >
>>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> es-discuss mailing list
>>>>>>> es-discuss at mozilla.org
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>>>>>>>
>>>>>>
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