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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)

How do I apply new documentation to legacy minified file?

I'm trying to apply new documentation to legacy code that is
Undocumented
Minified (We don't have the source code)
Included in the rest of the code via window.thing = thing in the minified file, instead of using modules and exports.
Used literally everywhere. It's the base framework for the entire web application.
My main intent is to get vsCode to display some intellisense for this module when I create a new page/file, rather than having to copy&paste code from other pages/files before it will tell me how to use the module's methods. And even then, it doesn't tell me how it works. Although after a few months I can now write this code somewhat reliably without looking, I've had to unravel the minified file some to find all the methods and properties available. I should be copy&pasting imports, not the whole damn file. We're also bringing in new developers soon, and (although coworkers disagree), I want to have something more for them to look at then just 'follow the pattern on the other pages'.
We are using webpack and have the ability to use modules. I prefer the module pattern, but it is clear that those who came before us did not. Using window.thing to use the module between files. My coworkers prefer to 'follow the pattern already there', rather than trying to fix old code. I don't whole-heartedly disagree, but still. So I need to make this as unobtrusive as possible.
webapp/documentation/main.js
import './thing.js';
/**#type {thing}**/
var thing; // This does not work. `thing` is marked as any.
// So I changed the type to thingModule.
/**#type {thingModule}**/
var thing; // This works.
/**#type {thingModule}*/
window.thing; // This does not work.
/**#type {thingModule}**/
var thing = window.thing; // Works for thing
// But does not change window.thing
However, none of those above propagate into the next file.
webapp/view/someFile.js
import '../../documentation/main.js';
/**#type {thingModule}**/ var thing = window.thing;
// Cannot change below this line //
thing.addView(/*blah blah blah*/);
thing.doStuff();
This allows me to look up properties of thing. But it does change the code slightly. Not much, but just enough that it would be frowned upon if left in the code when committed. Plus, if I find other modules that need similar documentation, I don't want a growing import statement for just documentation.
I need to be able to include it in a single line that only provides documentation.
import '../../documentation/main.js';
// Cannot change below this line //
thing.addView(/*blah blah blah*/);
thing.doStuff();
In this case, thing is shown as ':any' instead of ':thingModule' like it needs to be.
tl;dr:
I need to assign the #typedef to window.thing and make the jsDoc definition propagate anywhere documentation is imported. And I need to not change the actual declaration of window.thing.

inline usage of import with typescript 1.6 and es6 syntax

I am looking at updating some older js libs I have to typescript using the ES6 conventions, however I have come across a stumbling point.
So historically when I loaded a JSON file dynamically I would do something like this:
this.someFunctionWhichDoesStuff = function() {
var config = require(theConfigDir); // theConfigDir was a variable
// ... other stuffs
}
This worked fine, and I would also in some cases dynamically include some modules from a folder too:
this.someFunctionWhichDoesStuff = function() {
var actualImplementationToUse = require(theDirectoryWithImplementation); // theConfigDir was a variable
// ... other stuffs
}
This allowed me to switch implementations based upon configuration at earlier points, and worked well enough. Key points to note here are that the resolvers for the modules are variables not static text and that they are being run inside of functions not at root level.
So with this in mind I went over to the es6 style module inclusion in TS and realised I cannot do the above, as this is not valid syntax:
public someFunctionWhichDoesStuff() {
import actualImplementationToUse from theDirectoryWithImplementation;
// ... other stuffs
}
And it makes sense, as I know ES6 modules need to statically resolve modules, so I am cool with that, however in the typescript 1.6 world I am unsure how to resolve this as var includedModule = require(theDirectory); seems to be invalid as it doesnt know about require, which may be solved with inclusion of the node js d.ts file, however I was hoping someone could give some steering as to what the desired approach is in the new es6 world going forward?

sure I know I can do this, but is there a more es6 way of doing this? i.e if I use require I am locked into using require on all consumers (be it browser or node), I imagine there isn't but I just wanted to check before I went down this route.
ES6 spec doesn't specify a module loader anyways (SystemJS is just a sample non-standard implementation) and mostly you want to transpile down to es5. So using require is not a bad idea (especially for non .ts/.js files)

How does es6 module loading work

I've been reading about es6 module loaders and I just don't quite understand how it works and am hoping someone can enlighten me.
In the practical workflows link above they have an example like this
System.import('app/app').then(function(app) {
// app is now the Module object with exports as getters
});
No problem with that - I get it. But then I see stuff like this
var $ = require('jquery');
and get really confused. What happens if at the time of this call jquery has not yet been transferred to the browser? Does the thread just spin? Does the browser parse your script behind-the-scenes and reform it into a callback like RequireJs does? Is what it does configurable? Are there specific limitations?
Can someone give me a rundown?

The ES6 Module Loader will fetch the source, determine dependencies, and wait until those dependencies have loaded before executing the module. So by the time the require executes, the dependency is already sitting there waiting to be executed.
When loading CommonJS through an ES6 module loader, we rely on statically parsing out the require statements from the source, and only executing the source once those requires have loaded.
In this way we can support CommonJS in the browser loaded dynamically. Circular references are treated identically to the way they are handled in Node.
The regular expressions parsing out the require are actually pretty reliable and quick, while taking into account comments and surrounding tokens. See https://github.com/systemjs/systemjs/blob/master/lib/extension-cjs.js#L10 for the one used by SystemJS.
There is one remaining limitation with this approach and that is dynamic and conditional CommonJS requires like if (condition) require('some' + 'name') aren't detected properly. This is a necessary cost though to make CommonJS behave as a fully asynchronous module format in the browser.

TypeScript use typescript-require shared files

I use TypeScript to code my javascript file with Object Oriented Programing.
I want to use the node module https://npmjs.org/package/typescript-require to require my .ts files from other files.
I want to share my files in both server and client side. (Browser) And that's very important. Note that the folder /shared/ doesn't mean shared between client and server but between Game server and Web server. I use pomelo.js as framework, that's why.
For the moment I'm not using (successfully) the typescript-require library.
I do like that:
shared/lib/message.js
var Message = require('./../classes/Message');
module.exports = {
getNewInstance: function(message, data, status){
console.log(requireTs);// Global typescript-require instance
console.log(Message);
return new Message(message, data, status);
}
};
This file need the Message.js to create new instances.
shared/classes/Message.ts
class Message{
// Big stuff
}
try{
module.exports = Message;
}catch(e){}
At the end of the fil I add this try/catch to add the class to the module.exports if it exists. (It works, but it's not really a good way to do it, I would like to do better)
If I load the file from the browser, the module.export won't exists.
So, what I did above is working. Now if I try to use the typescript-require module, I'll change some things:
shared/lib/message.js
var Message = requireTs('./../classes/Message.ts');
I use requireTs instead of require, it's a global var. I precise I'm using .ts file.
shared/classes/Message.ts
export class Message{
// Big stuff
}
// remove the compatibility script at the end
Now, if I try like this and if I take a look to the console server, I get requireTs is object and Message is undefined in shared/lib/message.js.
I get the same if I don't use the export keyword in Message.ts. Even if I use my little script at the end I get always an error.
But there is more, I have another class name ValidatorMessage.ts which extends Message.ts, it's not working if I use the export keyword...
Did I did something wrong? I tried several other things but nothing is working, looks like the typescript-require is not able to require .ts files.
Thank you for your help.

Looking at the typescript-require library, I see it hasn't been updated for 9 months. As it includes the lib.d.ts typing central to TypeScript (and the node.d.ts typing), and as these have progressed greatly in the past 9 months (along with needed changes due to language updates), it's probably not compatible with the latest TypeScript releases (just my assumption, I may be wrong).
Sharing modules between Node and the browser is not easy with TypeScript, as they both use very different module systems (CommonJS in Node, and typically something like RequireJS in the browser). TypeScript emits code for one or the other, depending on the --module switch given. (Note: There is a Universal Module Definition (UMD) pattern some folks use, but TypeScript doesn't support this directly).
What goals exactly are you trying to achieve, and I may be able to offer some guidance.

I am doing the same and keep having issues whichever way I try to do things... The main problems for me are:
I write my typescript as namespaces and components, so there is no export module with multiple file compilation you have to do a hack to add some _exporter.ts at the end to add the export for your library-output.js to be importable as a module, this would require something like:
module.exports.MyRootNamespace = MyRootNamespace
If you do the above it works, however then you get the issue of when you need to reference classes from other modules (such as MyRootNamespace1.SomeClass being referenced by MyRootNamespace2.SomeOtherClass) you can reference it but then it will compile it into your library-output2.js file so you end up having duplicates of classes if you are trying to re-use typescript across multiple compiled targets (like how you would have 1 solution in VS and multiple projects which have their own dll outputs)
Assuming you are not happy with hacking the exports and/or duplicating your references then you can just import them into the global scope, which is a hack but works... however then when you decide you want to test your code (using whatever nodejs testing framework) you will need to mock out certain things, and as the dependencies for your components may not be included via a require() call (and your module may depend upon node_modules which are not really usable with global scope hacking) and this then makes it difficult to satisfy dependencies and mock certain ones, its like an all or nothing sort of approach.
Finally you can try to mitigate all these problems by using a typescript framework such as appex which allows you to run your typescript directly rather than the compile into js first, and while it seems very good up front it is VERY hard to debug compilation errors, this is currently my preferred way but I have an issue where my typescript compiles fine via tsc, but just blows up with a max stack size exception on appex, and I am at the mercy of the project maintainer to fix this (I was not able to find the underlying issue). There are also not many of these sort of projects out there however they make the issue of compiling at module level/file level etc a moot point.
Ultimately I have had nothing but problems trying to wrestle with Typescript to get it to work in a way which is maintainable and testable. I also am trying to re-use some of the typescript components on the clientside however if you go down the npm hack route to get your modules included you then have to make sure your client side uses a require compatible resource/package loader. As much as I would love to just use typescript on my client and my server projects, it just does not seem to want to work in a nice way.

Solution here:
Inheritance TypeScript with exported class and modules
Finally I don't use require-typescript but typescript.api instead, it works well. (You have to load lib.d.ts if you use it, else you'll get some errors on the console.
I don't have a solution to have the script on the browser yet. (Because of export keyword I have some errors client side) I think add a exports global var to avoid errors like this.
Thank you for your help Bill.