如何在 CommonJS 中使用 ES6 模块？

Question

I've seen Importing ES6 modules in CommonJS Node app? How to use ES6 modules with commonjs and https://nodejs.org/api/esm.html#esm_enabling

And I still don't get it. Fairly new to javascript.

The fundamental question is "What do I need to do and where do the bits go that enable me to use ES6 modules inside CommonJS?

Answer 1

In Node.js, if you want to import an ES module in a CommonJS module you can use dynamic import and the .mjs file extension on the ES modules. For example:

index.js CommonJS

const crypto = require('crypto');  // to show this is a commonJS module

import('./path/to/mod.mjs').then(mod =>
  console.log(mod.msg);    //  "Hello world!"
);

mod.mjs ES module

export const msg = "Hello world!";

Answer 2

Adding "type": "module" to the package.json enables ES 6 module. So in your package.json file add "type": "module" (or change it from "type": "commonjs" ). Changing this will enable ES6 modules and allow your source code to use import syntax.

Answer 3

ESModules and CommonJS are mutually exclusive, so you can't "use ES6 modules inside CommonJS".

However, in a way, you can "use CommonJS inside ESModules", if by "CommonJS" you only mean the require() function. You can create an instance of require() function with module.createRequire() :

import { createRequire } from 'module';
const require = createRequire(import.meta.url);

// sibling-module.js is a CommonJS module.
const siblingModule = require('./sibling-module');

There's a chapter in NodeJS's documentation on interoperability between the two module systems . It's very helpful, you might want to check it out.