# babel-plugin-transform-es2015-modules-commonjs

> This plugin transforms ES2015 modules to [CommonJS](http://wiki.commonjs.org/wiki/Modules/1.1).

## Example

**In**

```javascript
export default 42;
```

**Out**

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

exports.default = 42;
```

## Installation

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

## Usage

### Via `.babelrc` (Recommended)

**.babelrc**

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

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

### Via CLI

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

### Via Node API

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

## Options `loose`

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.

```javascript
var foo = exports.foo = 5;

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

In environments that don't support this you can enable loose mode on `es6.modules`
and instead of using `Object.defineProperty` an assignment will be used instead.

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