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Is it possible to use both CommonJS and ES6 module in a Node.JS command-line program?

I'm working on a CLI tool. I used "commander", which is a CommonJS module, to parse command-line arguments. I also want to use "p-map" to manage concurrency. However, "p-map" is a ES6 module.
Also I'm using Typescript.
Now both code editor and Typescript compiler won't complain. However I cannot execute my CLI tool. If I compile with "module":"commonjs", node would not load p-map and complains "Must use import to load ES Module... node_modules/p-map/index.js...require() of ES modules is not supported.". If I compile with "module":"es2015", use "require" to import the CommonJS modules, and add "type":"module" in my package.json, node would complain "ReferenceError: require is not defined".
I love the flexibility of Typescript/Javascript, however, it's time like this makes me miss Java. Java might be too prissy, but I don't spend hours trying to figure out import / export......
So, is it possible to use both CommonJS and ES6 module in a Node.JS command-line program?

To enhance compatibility, the (moderately new) node esm loader can import cjs-modules (e.g. import identifier from 'cjs-module-name';).
The other way around doesn't work, you can't require an esm-module, but dynamic import should work, if really necessary.
A related read may be the statement from p-map's owner regarding the topic.

Using Rollup + Svelte with third party AMD libraries

I understand that Svelte can produce AMD output and find some details on how to do this in the docs. I can also find some info on how to configure Rollup to output AMD modules. But what about input? What do I need to do when I have AMD modules as dependencies?
For example, suppose I have two different third party libraries that are both distributed as AMD libraries and I want to use those libraries in my Svelte project. How would I need to modify eg. this nested components demo to allow these AMD modules to be used as dependencies in my Svelte components?
Also, am I able to configure whether I bundle these libraries together with my Svelte components? If so, where would I need to do that?
Note
I also raised this issue on Github.

AMD modules are a pain to convert to ES modules, so you may find it difficult to bundle them with Rollup. (There's rollup-plugin-amd but it comes with caveats.)
But you can easily treat them as external dependencies that get loaded separately — just import them as normal then configure Rollup:
// rollup.config.js
export default {
// ...
format: 'amd',
external: ['an-external-amd-module'],
paths: {
'an-external-amd-module': 'https://my-cdn.com/an-external-amd-module.js'
}
};
You can see a demo here (repo here) — note that we're loading an exernal AMD module called the-answer, even though it's a regular import, because of the Rollup config.

Best way of including commonjs modules in a project using requirejs

I using requirejs to manage the javascript files in my project. However, there are some external libraries I want to use that do not adhere to the AMD format. A library I want to include is barba.js. How would this be done using the package loading feature of requirejs? Ideally I want to include a commonjs module without running a conversion tool.

Barba doesn't use the CommonJS module format.
Barba uses the UMD (Universal Module Definition) module format. This means that it is compatible with both the AMD module loading (as used by RequireJS) and CommonJS module loading (as used by Node.js).
So, that means you can just include Barba - or any other module in UMD format - with RequireJS the same way you include an AMD module:
define([
"barba/barba"
], function(Barba) {
Barba.Pjax.start(); // You can use Barba here
});

From requireJS doc.
define(function(require, exports, module) {
//Put traditional CommonJS module content here
});
This should make everything alright for you. I'm really not sure if it's needed though.

How can I integrate custom module loading with webpack?

I'm using Webpack 1 for a frontend project and I have a legacy internal Javascript library which uses its own module system similar to AMD. A module is defined with a code similar to this:
MyLib.define('module id', ['my', 'module', 'deps'], function (my, module, deps) { /* module code */});
Then you can use the modules with a code like this:
MyLib.require(['dep1', 'dep2'], function (dep1, dep2) {});
I would like to be able to use MyLib along with all the other CommonJS modules I'm already using. Can webpack support this somehow?

As far as I know, Webpack doesn't support custom module formats (if someone else knows otherwise, I'd love to be proven wrong, though).
You perhaps could work around this by writing a Webpack loader or a Babel plugin that converts the syntax to one of the module formats that Webpack supports. The latter is what Babel used to do for ES6 imports before Webpack supported them out of the box - it'd just transform them into CommonJS require calls.

Do I still need a module loader if I'm using ES6 modules?

Unfortunately my knowledge of JavaScript module loaders is still growing and I'm trying to understand their relationship to the new ES6 Modules. As far as I can tell using a module loader like CommonJS or RequireJS using ES5 compliant JavaScript really needed the use of an asynchronous module loader to increase performance and load only as needed using the respective module loader's syntax.
However looking at the ES6 module documentation and reading other information, it appears to me that module loading is natively supported via the import and export keywords. If this is the case am I correct that ES6 JS modules natively support asynchronous module loading and therefore I do not need to use an additional tool like CommonJS or RequireJS?

it appears to me that module loading is natively supported via the import and export keywords.
Not exactly. The import and export declarations only define the dependencies and the interface of each module. They allow to statically extract strings that name the required modules, nothing else.
If this is the case, do I not need to use an additional tool like CommonJS or RequireJS?
No. You still need to use a loader for ES6 modules, which resolves the names or paths or whatever from the imports to actual module files and loads them with an implementation-dependent method.
There are many tools or toolchains available, examples for the different solutions are
webpack: bundles everything into one large script
System.js: loads single modules dynamically and asynchronously (similar to what require.js does)
native: node.js and web browsers are still figuring out how to support module loading without additional libraries
babel transpilation: you can convert ES6 modules to AMD or CommonJS format and use the known tools like require.js for these

As far as my understanding goes, ES6 supports the syntax for defining and importing modules. The actual act of importing the modules that are required are a job of the infrastructure.
In modern browsers (as of 2016 that is) do not have built in functionality to support module loading and as such you will still need something like SystemJS to do the actual loading.

ES6 JavaScript Files are inherently treated as a module. if you define anything in a .js file, it will only be visible within that file (local scope ). what export does is, it exposes the classes / variables defined as export, visible to outside. then you can import it to a another module. There are other ways to define modules such as using Commonjs or AMD etc.. . Module loaders are required if you want to dynamically lazy load modules. ex. Systemjs is a such a Dynamic Module loader. it will fetch the physical module file from server dynamically when it is requested, and will prevent having multiple loads the same file. in SPA application in past had to load everything at the beginning to it to work. with dynamic module loaders now we can have only the files we need to do the intended job. hope this will help you.
https://github.com/systemjs/systemjs