This is a short post on how to use ESM with app-module-path in a Node.js (6+) project.
Lots of benifits, easier to export/import modules.
Instead of:
const foo = require('app/foo');
module.exports = { foo, bar: 2 };We can now use:
import foo from 'app/foo';
export default { foo, bar: 2 };And we don't need to do:
exports = module.exports = Foo;
exports.bar = 'bar';We can just:
export default Foo;
export const bar = 'bar';A1: Not possible to run anything higher than Node 8.2 on AWS Lambda.
A2: Perhaps don't wan't/can't start Node process with flag --experimental-modules
# install esm
npm i esm -SAdd a new entry point (entry.js):
// Entry point for our application.
// Setup esm
require = require('esm')(module);
// Setup app-module-path
require('app-module-path/register');
module.exports = require('./old-entry-point');The app with require calls and module.exports will continue to work, but here
is a shortcut for how to convert to import and export. Of course, manual work is also going to be needed.
(VS Code is used as editor, don't know how to search/replace in other editors)
In VS Code RegExp Search Replace:
Search: const\s+(\w+)\s+=\s+require\('([^']+)'\);?
Replace: import $1 from '$2';
Search: module.exports =
Replace: export default
Search: exports.(\w+)\s+=\s+([^']+)?
Replace: export $1 $2
-const { sleep } = require('src/utils/promise-utils');
+import { sleep } from 'src/utils/promise-utils';
-const { expect } = require('chai');
+import { expect } from 'chai';To be able to setup esm with mocha, it was not enough to just --require esm in mocha.opts
or try to initialize esm in the test/bootstrap.js file.
Had to change the test script in package.json from:
-"test": "_mocha --recursive",
+"test": "node -r esm node_modules/.bin/_mocha --recursive",to make it work.
https://medium.com/web-on-the-edge/es-modules-in-node-today-32cff914e4b - ESM release post
https://nodejs.org/api/esm.html#esm_enabling
https://github.com/standard-things/esm
https://github.com/patrick-steele-idem/app-module-path-node