PostCSS BEM To JavaScript

Translates CSS classes to a JavaScript file so that you can use typed definitions of styling classes in React / Vue.js etc. It includes support for BEM / ITCSS / BEMIT syntax.

Why?

• Useful for IntelliSense lookup of CSS classes in your JavaScript.
• Type safety. Ensures you only use CSS classes that are available (avoid typos / using deprecated classes etc.)
• Rolls BEM modifiers into block and element strings e.g. my-block--large { ... } becomes MyBlock.$large === 'my-block my-block--large'.

BEM example (style.css):

.my-button { /* ... */ }
.my-button--primary { /* ... */ }
.my-button__link { /* ... */ }
.my-button__link--bold { /* ... */ }
.my-button__fancy-icon { /* ... */ }

Outputs style.css.js (and a .css.json variant too alongside unmodified input CSS):

module.exports = {
  MyButton: {
    $primary: 'my-button my-button--primary',
    link: {
      $bold: 'my-button__link my-button__link--bold',
      toString: function () { return 'my-button__link' }
    },
    fancyIcon: 'my-button__fancy-icon',
    toString: function () { return 'my-button' }
  },
  Grid: {
    item: 'grid__item',
    toString: function () { return 'grid' }
  }
}

Usage

Command line example:

postcss --use postcss-bem-to-js ./style.css --config postcss.config.json

And the postcss.config.json:

{
  "postcss-bem-to-js": {
    "prefixMap": {
        "ln-o-": "o",
        "ln-c-": "c",
        "ln-u-": "u"
    },
    "replace": {
        "@": "_",
        "\\/": "of",
        "*": "_x"
    }
  }
}

Config: replace

A map defining how to replace certain text/symbols in CSS with JavaScript variable naming friendly equivalents e.g.

{
  replace: {
    '@': '_',
    '\\/': 'of',
    '*': '_x'
  }
}

With this button@wide becomes button_wide, grid-1/2 becomes item1of2, and spacing*2 becomes spacing_x2.

Config: prefix map

You can also configure the plugin to accept a prefixMap to map namespaced (e.g. BEMIT) style naming to some other prefix e.g.

{
  prefixMap: {
    'o-ns-': 'o',
    'c-ns-': 'c',
    'u-ns-': 'u'
  }
}

Converts o-ns-foo to oFoo