babel-preset-airbnb/README.md

# babel-preset-airbnb

> A babel preset for transforming your JavaScript for Airbnb.

Currently contains transforms for all [stage 4](https://tc39.github.io/ecma262/) (ES2018) and [stage 3](https://github.com/tc39/proposals#active-proposals) syntax that is permitted in the [Airbnb Style Guide](https://github.com/airbnb/javascript). Please note that if usage of a stage 3 proposal is not explicitly mentioned in the Airbnb Style Guide, then it will not be enabled here. Additionally, stage 4 syntax that is excluded is as follows:
 - generators: `regenerator-runtime` is too heavyweight for our use.
 - `async/await`: `regenerator-runtime` is too heavyweight for our use, and [async-to-promises](https://www.npmjs.com/package/babel-plugin-async-to-promises) is not yet complete enough to be safely used.
 - async iterators: depends on both generators and `async function`s
 - lifted template literal restrictions: we do not use tagged template literals, nor implement custom DSLs, otherwise we would enable this.

## Install

```sh
$ npm install --save-dev babel-preset-airbnb
```

## Usage

### Via `.babelrc` (Recommended)

**.babelrc**

```json
{
  "presets": ["airbnb"]
}
```

### Via CLI

```sh
$ babel script.js --presets airbnb
```

### Via Node API

```javascript
require('@babel/core').transform('code', {
  presets: ['airbnb']
});
```

### Targeting Environments

This module uses @babel/preset-env to target specific environments.

Please refer to [@babel/preset-env#targets](https://babeljs.io/docs/en/babel-preset-env#targets) for a list of available options.

For a list of browsers please see [browserlist](https://github.com/ai/browserslist).

You may override our default list of targets by providing your own `targets` key.

```json
{
  "presets": [["airbnb", {
    "targets": {
      "chrome": 50,
      "ie": 11,
      "firefox": 45
    }
  }]]
}
```

The following transpiles only for Node v6.

```json
{
  "presets": [["airbnb", {
    "targets": {
      "node": 6
    }
  }]]
}
```

If you wish, you can also inherit our default list of browsers and extend them using `additionalTargets`.

```json
{
  "presets": [["airbnb", {
    "additionalTargets": {
      "chrome": 42,
      "ie": 8
    }
  }]]
}
```

You may override our default debug option by providing your own `debug` key.

```json
{
  "presets": [["airbnb", {
    "debug": true
  }]]
}
```

## React Development Mode

When `process.env.NODE_ENV` is `'development'`, [the `development` mode will be set for `@babel/preset-react`](https://babeljs.io/docs/en/babel-preset-react#development).

You may override our default development option by providing your own boolean `development` key.

```json
{
  "presets": [["airbnb", {
    "development": false
  }]]
}
```

## React PropTypes removal

This preset can be configured to remove propTypes using [babel-plugin-transform-react-remove-prop-types](https://github.com/oliviertassinari/babel-plugin-transform-react-remove-prop-types) with the following default options:


To enable this transformation with the default options, set the `removePropTypes` option to `true`:

```json
{
  "presets": [["airbnb", {
    "removePropTypes": true
  }]]
}
```

The default options that will be used are:

```js
{
  mode: 'wrap',
  additionalLibraries: ['airbnb-prop-types'],
  ignoreFilenames: ['node_modules'],
}
```

Default options can be overridden using the `removePropTypes` option. These options will be shallow-merged with the defaults:

```json
{
  "presets": [["airbnb", {
    "removePropTypes": {
      "mode": "remove"
    }
  }]]
}
```

For example, if you are using this plugin in a deployable app, you might want to use the remove mode for your production build (and disable this transform entirely in development for optimal build speeds).

## Classes loose mode

By default, this preset will compile classes in normal mode. This is safer, but comes with a bundle size and runtime overhead. To [compile classes in loose mode](https://babeljs.io/docs/en/babel-plugin-transform-classes#loose), set the `looseClasses` option to `true`:

```json
{
  "presets": [["airbnb", {
    "looseClasses": true,
  }]]
}
```

The [risks of enabling loose classes are outlined in the Babel docs](https://babeljs.io/docs/en/babel-plugin-transform-classes#loose).

## Specifying a babel runtime version

By default @babel/plugin-transform-runtime will [assume the oldest version of the runtime](https://github.com/babel/babel/blob/e6264a09921c60b8f18870d0a75678e4fa04f0f8/packages/babel-plugin-transform-runtime/src/index.js#L42) to avoid importing helpers that don't exist which would fail at runtime. This can result in newer helpers being inlined into modules (ex. objectSpread2) which increases bundle size.

To avoid this you can configure the preset to use the same version of the runtime that's installed in your package.json.

ex. If package.json has `"@babel/runtime": "^7.5.5"` then you can use:

```json
{
  "presets": [["airbnb", {
    "runtimeVersion": "7.5.5",
  }]]
}
```

Note that this will result in a runtime breakage if the version passed into the airbnb preset is newer than the version of the babel runtime actually being used at build time.

## Disabling `plugin-transform-runtime`

You can use the `transformRuntime` option to disable [`@babel/plugin-transform-runtime`](https://babeljs.io/docs/en/babel-plugin-transform-runtime). Specifying `false` will disable the plugin. This option defaults to `true`.

## Specifying module transforms

You can use the `modules` option to enable transformation of modules given to this preset:

```json
{
  "presets": [["airbnb", {
    "modules": "auto"
  }]]
}
```

Both `true` and the option default `auto` will not transform modules if ES6 module syntax is already supported by the environment, or `"commonjs"` otherwise. `false` will not transform modules.

You can use the `runtimeHelpersUseESModules` option to prevent transformation of runtime helpers to CommonJS modules.

```json
{
  "presets": [["airbnb", {
    "runtimeHelpersUseESModules": true
  }]]
}
```

`true` will not transform runtime helpers to CommonJS modules. `false` will transform runtime helpers to CommonJS modules. The option defaults to `true` if `modules` is set to `false`, and `false` otherwise.