Babel.js is a command line tool that lets you transpile ES6 code into ES5 code that runs in current JavaScript environments, including Node.js and browsers.

Quick Install

# To install globally
$ npm install -g babel

# to install locally per package
$ npm install --save-dev babel

Use babel-node for Node.js:

# Using Nod
$ babel-node
 Object.assign({}, {message: 'hell yeah\'});  // => { message: 'hell yeah!' }

You need babel and browserify if you want to run ES6 on browsers

$ npm install --save-dev babelify browserify

To use Object.assign() and, etc. in browsers:

$ npm install --save core-js

At the top of your js file:



Use ESLint to lint your code in ES6:

$ npm install --save-dev eslint


Compile ES6 code to ES5:

$ babel script.js --out-file script-compiled.js

To compile from a directory, use -d option:

$ babel -d build-dir source-dir

To setup debugger work properly:

$ babel -d build-dir source-dir -s

To compile for the browser, install browserify and browser-run.

npm install -g browserify browser-run
browserify -t babelify script.js | browser-run -p 8080

Compile a bundle:

$ browserify script.js -t babelify --outfile bundle.js

Using Existing Modules

Import modules using ES6 syntax:

import 'core-js'; // Node module
import harness from './harness'; // ES6 module


Add to package.json:

"scripts": {
  "lint": "eslint source",
  "clean": "rm -rf build/* && mkdir build/public && mkdir build/server && mkdir build/client",
  "build-server": "babel -d build/server source/server -s",
  "build-client": "browserify source/client/index.js -t babelify --outfile build/client/bundle.js",
  "build": "npm run clean && npm run build-server && npm build-client"