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Check to see if dynamic import is a module in JavaScript/TypeScript

I am working on a ScriptManager class for a project that was created many years ago. The original code read scripts from a database, and these scripts are different depending on the customer and installation (the application is a desktop app that uses Chrome Embedded Framework to display web pages). The code would read custom JavaScript code and eval() it, which of course is highly undesirable.
I am replacing this code with a ScriptManager class that can support dynamically inserted code, and the ScriptManager is capable of loading code as a module using JavaScript's dynamic import() command, or loading code as pure script by creating a script tag dynamically in the document.
My problem is that there are many different possible custom code blocks in the database, and not all are modules; some will be pure script until those can be converted to modules at a later time. My code can handle this as described above, but I need a way to detect if the script code from the database is a module, so I can either use the import() command or insert a script tag if it is not.
I am solving this temporarily by making sure any module script code has "export const isModule = true", and checking this after calling import(). This works, but any code that is pure script still results in a module variable, but with no exports in it. If possible I don't want the other developers to have to remember to add isModule = true to any modules they develop in the future.
Is there a way to check that code is a module without having to do complex analysis of the code to check if there are exports in it? Since import() still returns an object and throws no errors if there are no exports, I don't know how to detect this.
UPDATE: Here are some examples of how this is intended to work:
// Not real code, pretend that function gets the string of the script.
let code = getSomeCodeFromTheDatabase();
// Save the code for later loading.
let filename = 'some-filename.js';
saveCodeToFile(code, filename);
// Attempt to dynamically import the script as a module.
let module = await import(filename);
// If it is NOT a module, load it instead as a script tag.
// This is where I need to be able to detect if the code is
// a module or pure script.
if (!module.isModule) {
let scriptTag = document.createElement('script');
scriptTag.src = filename;
document.head.appendChild(script);
}

So if you look here How can I tell if a particular module is a CommonJS module or an ES6 module? you will see I answered a similar question.
So the thing is Sarah, modules are defined by the way that they resolve. Module-types resolving differently is what, not only makes them incompatible with one another, but it is also why we name them differently. Originally Transpillers like Babel & TypeScript were invented because of differences in ECMA-262 Specifications, and the desire to support people who didn't have the updated specifications, as well as supporting the newer features for those who did.
Today transpilers are still being used, conceptually, much the same way. They still help us maintain a single code base while supporting older specifications, and features in newer specifications, at the same time, but the also have the added benefit of being able to generate multiple different builds from a single code base. They use this to support different module types. In node.js, the primary module-type is CJS, but the future lies in ESM modules, so package maintainers have opted to dual build the projects. The use the TypeScript Compiler (aka Transpiler) to emit a CJS build, and an ESM build.
Now this is where things get complicated, because you cannot tell just by looking at a module if it CJS or ESM in this situation, **you absolutely have to inspect its code, and check if it has more than one tsconfig.json file (because it would need at-least 2 to maintain a bi-modular build (which are becoming increasingly common with the turn of each day)
My Suggestion to You:
Use well documented packages. Good packages should be documented well, and those packages should state in their README.md document, what type of package/module they are, and if the package supports more than one module type. If in doubt you can either come and ask here, or better yet, you can ask the maintainer by creating an issue, asking them to add that information to their README.md document.

You can check that there are no export after import. In chrome import() added empty default for non module.
function isNotModule(module) {
return (!Object.keys(module).length) || (!!module.default && typeof module.default === 'object' && !Object.keys(module.default).length)
}
import('./test.js')
.then((module) => {
console.log('./test.js',isNotModule(module))
})
May be it's better to check source code via regex to check if it contains export
something like this
const reg = new RegExp('([^\w]|^)export((\s+)\w|(\s*{))')
reg.test(source)

RequireJS: Difference between "requirejs" and "require" functions

I am using requireJS 2.x. I found out that some tutorials (and the official docs) sometimes use
requirejs.config({ [...] });
requirejs(["module"]) ...
and sometimes
require.config({ [...] });
require(["module"]) ...
Is there any difference between those two functions (require and requirejs)? I could not find any word about that in the docs. :(

They are exactly the same.
The reason is some environments might already have a require, in which case RequireJS doesn't overwrite it and allows usage of the library through requirejs
See this commit - https://github.com/jrburke/requirejs/commit/be45948433b053921dc6a6a57bf06d04e13b3b39

Are requirejs And require the Same?
As of RequireJS 2.1.15, require and requirejs in the global space are indeed "exactly the same", as can be evidenced by this test you can perform in the console:
> require === requirejs
true
That the test returns true tells you they are the exact same function object. They are not two functions that happen to have similar or identical code. They are the same object, period.
Note, however when you execute define(['require'], function (require) { The require passed to the function is normally different from the global require.
Should You Use require or requirejs?
It depends. RequireJS is an AMD loader but it is not the only loader in town. If you want to write code that conforms 100% to the AMD spec, so that someone using your code can use whatever loader they want without having to modify your code, then you should use require at the global level, because requirejs is specific to RequireJS. Another AMD loader won't define it. The AMD spec defines require but not requirejs.
If you are loading something else that defines a global require then you have to use requirejs at the global level to avoid conflict.
Inside a module, always use define to obtain a reference to require. You should do this quite irrespective of whether there is a conflict in the global space.

OK, they may indeed be "exactly the same". Let's then focus on why you would use one versus the other...
What is unclear is what should be considered "best practice": If requirejs provides extra assurance "if some environments might already have a require", then wouldn't it be a good idea to always use the requirejs function to define a require configuration rather than the require function?
Also, what happens if the unthinkable happens and the environment in question not only already has a "require" defined but also has a "requirejs" defined? Does that mean we should have a requirejsjs too? And so on...?

They are Same
Open website which loaded require already
then open Chrome console
type require in console and press enter
type requirejs in console and press enter
you can find that they are same function with different names

Why do concatenated RequireJS AMD modules need a loader?

We love RequireJS and AMD during development, where we can edit a module, hit reload in our browser, and immediately see the result. But when it comes time to concatenate our modules into a single file for production deployment, there apparently has to be an AMD loader still present, whether that loader is RequireJS itself or its smaller partner “almond” as explained here:
http://requirejs.org/docs/faq-optimization.html#wrap
My confusion is: why is a loader necessary at all? Unless you have very unusual circumstances that make it necessary for you to make require() calls inside of your modules, it would appear that a series of AMD modules could be concatenated without a loader present at all. The simplest possible example would be a pair of modules like the following.
ModA.js:
define([], function() {
return {a: 1};
});
ModB.js:
define(['ModA'], function(A) {
return {b : 2};
});
Given these two modules, it seems that a concatenator could simply produce the following text, and not burden the production server or browser with the extra bandwidth or computation required by either RequireJS or Almond.
I imagine a concatenator that produces (and I am using chevron-quotes «,» to show where the snippets from the two modules above have been inserted):
(function() {
var ModA = «function() {
return {a: 1};
}»();
var ModB = «function(A) {
return {b : 2};
}»(ModA);
return ModB;
})();
This, so far as I can see, would correctly reproduce the semantics of AMD, with a minimum of extraneous glue JavaScript. Is there such a concatenator available? If not, would I be a fool for thinking that I should write one — are there really very few code bases that consist of simple and clean modules written with define() and that never need further require() calls inside that kick off later asynchronous fetches of code?

An AMD optimiser has the scope to optimise more than the number of files to be downloaded, it can also optimise the number of modules loaded in memory.
For example, if you have 10 modules and can optimise them to 1 file, then you have saved yourself 9 downloads.
If Page1 uses all 10 modules then that's great. But what if Page2 only uses 1? An AMD loader can delay the execution of the 'factory function' until a module is require'd. Therefore, Page2 only triggers a single 'factory function' to execute.
If each module consumes 100kb of memory upon being require'd, then an AMD framework that has runtime optimisation will also save us 900kb of memory on Page2.
An example of this could be an 'About Box' style dialog. Where the very execution of it is delayed until the very last second as it won't be accessed in 99% of cases. E.g. (in loose jQuery syntax):
aboutBoxBtn.click(function () {
require(['aboutBox'], function (aboutBox) {
aboutBox.show();
}
});
You save the expense of creating the JS objects and DOM associated with the 'About Box' until you are sure it's necessary.
For more info, see Delay executing defines until first require for requirejs's take on this.

The only real benefit is if you use modules across sections so there's a benefit to caching modules independently.

I had the same need, so I created a simple AMD "compiler" for that purpose that does just that. You can get it at https://github.com/amitayh/amd-compiler
Please note that it has many features missing, but it does the job (at least for me). Feel free to contribute to the codebase.

In case you compile you code with require.js into a single large file for production, you can use almond.js to completely replace require.
Almond only handles the module references management not the loading itself which is no longer needed.
Be careful of the restrictions almond imposes in order to work

There is no reason why there couldn't be a build tool such as the one you propose.
The last time* I looked at the optimizer's output, it converted the modules to explicitly named modules, and then concatenated those together. It relied on require itself to make sure that the factory functions were called in the right order, and that the proper module objects were passed around. To build a tool like you want, you would have to explicitly linearize the modules -- not impossible, but a lot more work. That's probably why it hasn't been done.
I believe** that the optimizer has a feature to automatically include require itself (or almond) into the built file, so that you only have to have one download. That would be larger than the output of the build tool you want, but otherwise the same.
If there was a build tool that produced the kind of output you're asking for, It would have to be more careful, in case of the synchronous require, the use of exports instead of return, and any other CommonJS compatibility features.
*That was a few years ago. 2010, I think.
**But can't seem to find it right now.

Curl throwing ‘Promise already completed’ error

I’m currently testing various asynchronous-resource-loaders to see which one I want to use. At the moment Curl is throwing a ‘Promise already completed’ error…and their documentation says ‘this should never happen’.
I “suspect” I must to use a ‘define’ within each file being loaded (hope not). Further, their documentation says Curl can work with non-AMD javascript files. But...I am new to AMD and since Curl is far-faster than the other ones I'm testing...I am willing to put some time into understanding this better.
Lastly...
Even though FireBug shows the errors...all the files STILL LOAD asynchronously! But, BECAUSE there are errors...the 'then' portion of the code never gets called.
So My Questions Are:
Do I have to update all the JavaScript file-objects to be contained in a 'define'? (...hope not)
Can you see any other problem syntactically?
The Head’s Code Looks Like This:
<script type="text/javascript">
///<summary>Configuration</summary>
curl = { baseUrl: 'Includes/JavaScript/' };
</script>
<script src="Loaders/Curl/curl.js" type="text/javascript"></script>
<script type="text/javascript">
function onSuccess() {
}
function onError(ex) {
//alert(ex);
}
require(["MooTools/Core/mootools-1.2.2-core-jm",
"MooTools/mGeneral",
"jQuery/Core/jquery-1.3.2",
"jQuery/Core/jquery.tools.min",
"jQuery/ThirdPartyPlugIns/jquery.tmpl"])
.then(onSuccess, onError);
//require(["jQuery/TopUp/top_up-min"], null);
require(["jQuery/ThirdPartyPlugIns/jquery.dimensions",
"jQuery/ThirdPartyPlugIns/jQuery.Color.Animations",
"jQuery/ThirdPartyPlugIns/jquery.corners.min",
"jQuery/ThirdPartyPlugIns/jquery.tipsy",
"jQuery/ThirdPartyPlugIns/jquery.numberformatter-1.1.0",
"jQuery/ThirdPartyPlugIns/jquery.tipsy"]);
require(["general",
"WindowCenter",
"ThirdPartyPlugin/KeyBoardCapture",
"ThirdPartyPlugin/bsn.AutoSuggest_2.1.3",
"ee/8Ball",
"ee/EE"]);
</script>
Again...I'm sure it is caused by inexperience with AMD-styled code, but I still need help...so any is appreciated.

Typically, you should wrap your modules in a define() or append a define() at the end of the file if those modules have no dependencies. It seems, though, that those modules all depend on jQuery, if not other modules/files.
Since you're not using standard AMD require()/define() protocol, AMD is not really helping you with these modules. Unless you plan to write your own modules using define(), then you could use just about any async loader.
That said, there is a way to make curl.js work with non-AMD modules/files. Use the js! plugin. Here's your first block of files translated to use the js! plugin (note I also added the ".js" ext back on which I like to do with non-modules):
// we load the core files first, then get the next block that depends on them
curl([
"js!MooTools/Core/mootools-1.2.2-core-jm.js",
"js!jQuery/Core/jquery-1.3.2.js"
]).next([
"js!MooTools/mGeneral.js",
"js!jQuery/Core/jquery.tools.min.js",
"js!jQuery/ThirdPartyPlugIns/jquery.tmpl.js"
]).then(onSuccess, onError);
If any of those files within each array depend on each other, you can also use the !order suffix on them to ensure they wait for other files before executing/evaluating (be sure you're setting proper cache headers, though). Actually, the !order suffix is the fastest method as long as there are no caching issues (mobile browsers add some additional constraints on file size).
Were there any other error messages? Specifically, I would expect curl.js to throw at least one error besides just "Promise not completed".
Also, please check the Net tab (Firebug) or the Network tab (Chrome) to check that curl.js is looking in the correct location for the modules.
FWIW, I am planning to remove the alias require --> curl. The reason is that the global require function is non-standard (and explicitly not standardized in the AMD proposal). I suggest you use curl() instead of require().
curl.js also allows it's top-level api to be aliased explicitly via the "apiName" config param if you really, really want to use the name "require". :)
<script>curl = { apiName: "require" }; </script>
<script src="path/to/curl.js"></script>
<script>require(["some/modules"]).then(success, failure);</script>
More FWIW: the standard require is typically only needed in a module and can be requested by including it as a dependency:
define(["require"], function (require) {
require(["another/module"], function (another) {
// use another module here
});
});
-- John

If you're only doing normal javascript file loading (not modules), as it appears, i would encourage you to check out LABjs (http://labjs.com). LABjs focuses on being the most performance optimized loading solution (to the exclusion of some other features like module/dependency style stuff).
In fact, LABjs 2.0a (https://github.com/getify/LABjs/blob/master/next/LAB.src.js), which will be fully released in the next few days, is really exceptionally fast (even more than 1.2) at loading general scripts in parallel. I encourage you to give it a try, unless (as John eludes to above) you plan to go to module syntax... then stick with Curl or RequireJS.

Getting started with Yabble--browser-side CommonJS module loading

Is anyone familiar with Yabble or other browser-side CommonJS loaders?
I'm experimenting with Node.js and would very much like to create Javascript modules which can be used interchangeably on the server side and the client side. This may end up being more a "because it's awesome" kind of thing more so than "because it's practical and useful" kind of thing.
As such, I'm basically trying to get the CommonJS require() method to work on the browser-side, which is exactly what Yabble is supposed to do. I don't really know where to start with it though. I can't seem to find any documentation other than what's found in Yabble's Github readme, and that's not helping much.
Essentially all I've done is put this in an HTML page...
<script src="yabble.js"></script>
<!-- Uses require -->
<script>
require.setModuleRoot('http://localhost:8030/')
my_module = require('my_module')
</script>
But anytime I call the require() function all I get a Synchronous require() is not supported. exception thrown.
Can someone help me get started? Where am I supposed to load yabble.js where am I supposed to call require? Is there a special way to run my Javascript modules?

When loading Javascript code that will need to use the require() function into the browser, the entry point into that code must be the require.run() function.
e.g., Good:
<script src="yabble.js"></script>
<script>
require.setModuleRoot('http://localhost:8030/')
require.run('my_module') // <-- Uses require() function somewhere
</script>
e.g., Bad (Will get the Synchronous require() is not supported error):
<script src="yabble.js"></script>
<script src="http://localhost:8030/my_module.js"></script> <!-- <== Use's require function somewhere -->
FYI, it's pretty nifty how Yabble does this. It will actually statically analyze your Javascript source code, I think basically just using a regular expression to look for the require() method, and then try to pull that .js script from the server, then it does the same static analysis of that .js script, and on and on.
This can be particularly confusing because it will actually load those .js scripts even if the control logic would mean program flow would never reach the require() function. e.g., if you had...
if (False) { require('some_module'); }
... Yabble will still load this module.

Synchronous loading of modules in the browser is problematic. A construct like:
var x = require('something_remote.js')
Implies that the browser will halt your code (i.e. block), go and fetch the remote file, parse it, and then return to you the exports. But this does not jive with the single-threaded browser environment - we would be halting the main JavaScript thread (and thus page interactivity for the user) on the performance of the network. So browsers have evolved against this scenario, to favor async loading on their own schedule. There is some good discussion here:
http://www.sitepen.com/blog/2010/07/16/asynchronous-commonjs-modules-for-the-browser-and-introducing-transporter/
One pattern which might work here is that a require() implementation does synchronously block, fetches the file via XHR and then evals it, but that seems to run against all the browser support/infrastructure for async file-based loading. Also I'm curious what implications that would have for the cross-domain primitive of browser security.
So in order to fit the browser async loading model, we'll need to use a callback mechanism like:
require("something.js", function () { // called later, after something.js has loaded! })
It looks like RequireJS is doing this:
http://requirejs.org/docs/start.html
Perhaps give that a shot?
JavaScript environments like NodeJS etc - built with the provision of loading "local" modules from disk, instead of foreign network hosts - can do the synchronous load.
I would greatly appreciate any corrections from JS experts :-)