# postcss-prefix-selector

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> Prefix every CSS selector with a custom namespace `.a => .prefix .a`

## Table of Contents

- [Install](#install)
- [Usage with PostCSS](#usage-with-postcss)
- [Usage with Webpack](#usage-with-webpack)
- [Options](#options)
- [Maintainer](#maintainer)
- [Contribute](#contribute)
- [License](#license)

## Install

```console
$ npm install postcss-prefix-selector
```

## Usage with PostCSS

```js
const prefixer = require('postcss-prefix-selector')

// css to be processed
const css = fs.readFileSync("input.css", "utf8")

const out = postcss().use(prefixer({
  prefix: '.some-selector',
  exclude: ['.c'],

  // Optional transform callback for case-by-case overrides
  transform: function (prefix, selector, prefixedSelector) {
    if (selector === 'body') {
      return 'body' + prefix;
    } else {
      return prefixedSelector;
    }
  }
})).process(css).css
```

Using the options above and the CSS below...

```css
body {
  background: red;
}

.a, .b {
  color: aqua;
}

.c {
  color: coral;
}
```

You will get the following output

```css
body.some-selector {
  background: red;
}

.some-selector .a, .some-selector .b {
  color: aqua;
}

.c {
  color: coral;
}
```

## Usage with webpack

Use it like you'd use any other PostCSS plugin. If you also have `autoprefixer` in your webpack config then make sure that `postcss-prefix-selector` is called first. This is needed to avoid running the prefixer twice on both standard selectors and vendor specific ones (ex: `@keyframes` and `@webkit-keyframes`).

```js
const prefixer = require('postcss-prefix-selector');

module: {
  rules: [{
    test: /\.css$/,
    use: [
      require.resolve('style-loader'),
      require.resolve('css-loader'),
      {
        loader: require.resolve('postcss-loader'),
        options: {
          plugins: () => [
            prefixer({
              prefix: '.my-prefix'
            }),
            autoprefixer({
              browsers: ['last 4 versions']
            })
          ]
        }
      }
    ]
  }]
}
```

## Options

- `prefix` - This string is added before every CSS selector.
- `exclude` - It's possible to avoid prefixing some selectors by passing an array of selectors (strings or regular expressions).
- `transform` - In cases where you may want to use the prefix differently for different selectors, it is possible to pass in a custom transform method.

## Maintainer

This project was originally created by [@jongleberry](https://github.com/jonathanong) and is being maintained by [@RadValentin](https://github.com/RadValentin). If you have any questions, feel free to ping the latter.

## Contribute

Please contribute! If you have any questions or bugs, [open an issue](https://github.com/RadValentin/postcss-prefix-selector/issues/new). Or, open a pull request with a fix.

This project uses Mocha. If you submit a PR, please add appropriate tests and make sure that everything is green for your branch.

## License

[MIT](LICENSE) © 2015-2017 Jonathan Ong.

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