babel-plugin-transform-modules-simple-commonjs

Simple transformer for ECMAScript 2015 modules (CommonJS).

Converts this code:

import x from '/path/to/x';
import y from '/path/to/y';
doSomething();
export default x + y;

Into this one:

var x = require('/path/to/x');
var y = require('/path/to/y');
doSomething();
module.exports = x + y;

Instead of this one (generated with babel-plugin-transform-es2015-modules-commonjs):

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

var _x = require('/path/to/x');

var _x2 = _interopRequireDefault(_x);

var _y = require('/path/to/y');

var _y2 = _interopRequireDefault(_y);

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

doSomething();
exports.default = _x2.default + _y2.default;

This supports all standard es2015 import and export code with some caveats.

Caveats

1. When exporting the final value is used, not the value when writing an export statement. It is not supported to mutate declarations that have been exported. You will not be warned, it will just not work.

2. You cannot export default and export a named item in the same file as module.exports assignment will conflict with the exports assignment. This transform will error if you attempt to do this.

3. If you mix default imports and importing *, it will work, but will not be valid in ES2015. E.g. with the following...

// file a
export default 1;

// file b
import * as a from './a';

// file c
export const c = 3;

// file d
import c from './c';

In the official Babel module, a in file b will be undefined and c in file d will be undefined. Using this module, they will be 1 and 3 respectively.

4. Updating the exports on-the-fly will not work. This is not supported within commonjs normally anyway, but is supported with the official plugin.

You may want to use a linter (such as eslint with eslint-plugin-import) in order to ensure that your code is standard whilst using this simplified transform.

Installation

$ npm install --save-dev babel-plugin-transform-modules-simple-commonjs

Usage

Via .babelrc (Recommended)

.babelrc

{
  "plugins": ["transform-modules-simple-commonjs"]
}

Via Node API

require('babel').transform('code', {
  plugins: ['transform-modules-simple-commonjs']
});

Options

The various transforms done by this module can be disabled individually. This is especially useful if you need this module to convert import statements into reasonable commonjs statements, but require the default Babel behavior for exported functions (which get hoisted to the beginning of the scope, thus always exporting correctly even if circular dependencies exist - for this set the exportNamed option to false).

.babelrc example: disable everything

{
  "plugins": [
    ["transform-modules-simple-commonjs", {
      "exportNamed": false,
      "exportDefault": false,
      "exportAll": false,
      "import": false
    }]
  ]
}

Additionally, setting the option inlineReplace:true will replace import statements with require statements on the same line, preserving any required order of operations, instead of the default behavior of moving all import-generated requires to the top of the file.

Usage with other plugins

By default, this replaces the functionality in @babel/plugin-transform-modules-commonjs, which needs to be disabled or after this plugin.