How to Enable ES6 Features in Node.js with Babel: A Practical Guide

Because Babel, WebPack and React are popular, developers like Xiao Ming have started using many ES2015 (ES6) features such as import, export, class, arrow functions, let and const, but Node.js still rejects import statements, leading to inconsistent code styles in the same repository.

Node.js Support for ES6

Node.js’s V8 engine classifies ES6 features into three levels: shipping (enabled by default), staged (requires the --harmony flag), and in‑progress (still experimental).

Shipping (enabled by default)

Block scoping

let (strict mode only)

const

function‑in‑blocks (strict mode only)

Classes (strict mode only)

Collections, Map, WeakMap, Set, WeakSet

Typed arrays

Generators

Binary and Octal literals

Object literal extensions (shorthand properties and methods)

Promises

New String methods

Symbols

Template strings

Arrow Functions

new.target

Object.assign

Spread operator

Staged (requires --harmony)

Symbol.toStringTag

Array.prototype.includes (polyfill available in 5.x)

Rest Parameters (transform‑es2015‑parameters can transpile, 5.x)

In‑progress (experimental)

--harmony_modules (enable "harmony modules")
--harmony_array_includes (enable "harmony Array.prototype.includes")
--harmony_regexps (enable "harmony regular expression extensions")
--harmony_proxies (enable "harmony proxies")
--harmony_sloppy (enable "harmony features in sloppy mode")
--harmony_unicode_regexps (enable "harmony unicode regexps")
--harmony_reflect (enable "harmony Reflect API")
--harmony_destructuring (enable "harmony destructuring")
--harmony_sharedarraybuffer (enable "harmony sharedarraybuffer")
--harmony_atomics (enable "harmony atomics")
--harmony_new_target (enable "harmony new.target")

Enabling ES6 in Node.js with Babel

Babel can transpile ES6 syntax that the current engine does not support. The typical workflow is to select a set of Babel plugins that cover the needed features.

Recommended plugins

transform‑strict‑mode (adds "use strict" automatically)

transform‑es2015‑modules‑commonjs (converts ES6 modules to CommonJS)

transform‑es2015‑spread (adds spread operator support)

transform‑es2015‑destructuring (adds destructuring support)

transform‑es2015‑parameters (adds default parameters, parameter destructuring, etc.)

Conversion example: import

import Mod from './mod';
new Mod();

transforms to

'use strict';
var _mod = require('./mod');
var _mod2 = _interopRequireDefault(_mod);
function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
new _mod2.default();

Conversion example: export

export default class Mod { }

transforms to

'use strict';
Object.defineProperty(exports, "__esModule", { value: true });
class Mod { }
exports.default = Mod;

Installation

# Install core and CLI
$ npm install --save-dev babel-core babel-cli
# Install all plugins
$ npm install --save-dev babel-plugin-transform-strict-mode babel-plugin-transform-es2015-modules-commonjs babel-plugin-transform-es2015-spread babel-plugin-transform-es2015-destructuring babel-plugin-transform-es2015-parameters

.babelrc configuration

{
  "plugins": [
    "transform-strict-mode",
    "transform-es2015-modules-commonjs",
    "transform-es2015-spread",
    "transform-es2015-destructuring",
    "transform-es2015-parameters"
  ]
}

Project structure and build commands

Place ES6 source files in a src directory and compile them to lib: babel src --out-dir lib During development you can run the code directly with:

babel-node src/index.js

package.json scripts

{
  "name": "my-awesome-es6-package",
  "version": "1.0.0",
  "description": "use es6 in node",
  "main": "lib/index.js",
  "scripts": {
    "start": "babel-node src/index.js",
    "build": "babel src --out-dir lib"
  },
  "devDependencies": {
    "babel-cli": "~6.3.17",
    "babel-core": "~6.3.26",
    "babel-plugin-syntax-object-rest-spread": "^6.3.13",
    "babel-plugin-transform-es2015-modules-commonjs": "^6.3.16",
    "babel-plugin-transform-es2015-spread": "^6.3.14",
    "babel-plugin-transform-object-rest-spread": "^6.3.13",
    "babel-polyfill": "^6.3.14"
  }
}

Remember to point the main field to the compiled file for end‑users, and avoid using babel-node in production.

Further reading

Node.js ES6 support documentation

Babel plugin list

ES6 compatibility tables