Node v13 / Jest / ES6 — native support for modules without babel or esm

Question

Is it possible to test ES6 Modules with Jest without esm or babel? Since node v13 supports es6 natively have tried:

//package.json {   …   "type": "module"   … }    //__tests__/a.js import Foo from '../src/Foo.js';   $ npx jest  Jest encountered an unexpected token … Details:  /home/node/xxx/__tests__/a.js:1 import Foo from '../src/Foo.js'; ^^^^^^  SyntaxError: Cannot use import statement outside a module 

When babel is added a transpiler, it works, but can es6 modules be used natively as well?

Answer 1

Yes, it is possible from [email protected]. From this version, there is a native support of esm, so you will not have to transpile your code with babel anymore.

It is not documented yet, but according to this issue you have to do 3 easy steps to achieve that (At the time of writing this answer):

• Make sure you don't transform away import statements by setting transform: {} in your jest config file
• Run node@^12.16.0 || >=13.2.0 with --experimental-vm-modules flag
• Run your test with jest-environment-node or jest-environment-jsdom-sixteen.

So your jest config file should contain at least this:

export default {     testEnvironment: 'jest-environment-node',     transform: {}     ... }; 

And to set --experimental-vm-modules flag, you will have to run Jest from package.json as follows (I hope this will change in the future):

"scripts": {     "test": "node --experimental-vm-modules node_modules/jest/bin/jest.js" } 

I hope, this answer was helpful to you.