ES2015 modules to CommonJS transform

Babel 6 Changes

Babel 6 changed some behavior by not doing module.exports = exports['default'] anymore in the modules transforms.

There are some caveats, but you can use babel-plugin-add-module-exports, so that updating to Babel 6 isn't a breaking change since users that don't use ES modules don't have to do require("your-module").default.

However, it may not match how Node eventually implements ES modules natively given the the current proposal.

This plugin transforms ES2015 modules to CommonJS.

CommonJS (CJS) Modules/1.1

Example

In

export default 42;

Out

Object.defineProperty(exports, "__esModule", {
  value: true
});

exports.default = 42;

Installation

npm install --save-dev babel-plugin-transform-es2015-modules-commonjs

Usage

Via .babelrc (Recommended)

.babelrc

// without options
{
  "plugins": ["transform-es2015-modules-commonjs"]
}

// with options
{
  "plugins": [
    ["transform-es2015-modules-commonjs", {
      "allowTopLevelThis": true
    }]
  ]
}

Via CLI

babel --plugins transform-es2015-modules-commonjs script.js

Via Node API

require("babel-core").transform("code", {
  plugins: ["transform-es2015-modules-commonjs"]
});

Options

loose

boolean, defaults to false.

As per the spec, import and export are only allowed to be used at the top level. When in loose mode these are allowed to be used anywhere.

And by default, when using exports with babel a non-enumerable __esModule property is exported.

var foo = exports.foo = 5;

Object.defineProperty(exports, "__esModule", {
  value: true
});

In environments that don’t support this you can enable loose mode on babel-plugin-transform-es2015-modules-commonjs and instead of using Object.defineProperty an assignment will be used instead.

var foo = exports.foo = 5;
exports.__esModule = true;

strict

boolean, defaults to false

By default, when using exports with babel a non-enumerable __esModule property is exported. In some cases this property is used to determine if the import is the default export or if it contains the default export.

var foo = exports.foo = 5;

Object.defineProperty(exports, "__esModule", {
  value: true
});

In order to prevent the __esModule property from being exported, you can set the strict option to true.

noInterop

boolean, defaults to false

By default, when using exports with babel a non-enumerable __esModule property is exported. This property is then used to determine if the import is the default export or if it contains the default export.

"use strict";

var _foo = require("foo");

var _foo2 = _interopRequireDefault(_foo);

function _interopRequireDefault(obj) {
  return obj && obj.__esModule ? obj : { default: obj };
}

In cases where the auto-unwrapping of default is not needed, you can set the noInterop option to true to avoid the usage of the interopRequireDefault helper (shown in inline form above).