ah-theyre-here-esm-nodejs

Code accompanying my talk "Aaaaaaaaaaaaaah, They’re Here! ES Modules in Node.JS", whose slides can be found here

Installing

You will need a Node.js version >= 13.2.

First, you install:

$ npm ci
...

Then, you build:

$ npm run build
...

This repository has code in src that is fully checked by tests in the test dir. To run the test, use:

$ npm test
...

The src directory contains all the code samples found in the talk:

01-what-are-es-modules: code that shows a sample of ES module syntax, along with its equivalent CommonJS code. This sample is not comprehensive by any moeans
02-strict: code that shows that ES modules are strict by definition, while CommonJS is not.
03-esm-is-browser-compatible: code that shows that the same ES module code can be used both in the browser and in Node.js, including the use of "import maps".
04-esm-is-statically-parsed code that shows that ES module problems are caught statically before execution of said code.
05-esm-is-async: code that shows sample "top-level await" code. This code does not (yet) run in Node.js and is not tested.
06-exports: code that shows how the "exports" field in package.json works
07-conditional-exports: code that shows how conditional exports work, and a sample dual-mode library that is automatically created from ESM code. See this section for more explanations.
08-migration: code that shows how to migrate CommonJS code to ES module code, bottom up or top down.

See this package source code for how to create an ESM package and automatically convert it to a dual-mode package with additional CJS files.

In essence:

The esm directory contains the source code itself, and a package.json that has "type": "module" in it. The "type: "module" is necessary because the names of the files in ESM and CJS must stay the same, and this is only possible if the extension is .js in both cases.
The build script uses babel to transpile the esm directory.
The .babelrc file includes only the specific plugins necessary to transpile import to package.json.
The package.json file includes the dependencies needed on babel* packages.
The package.json includes the "exports" for the dual-mode entry points in the esm and cjs directories.