cogs-transformer-local-css

A local CSS transformer for Cogs inspired by this blog post and works similarly to this webpack loader.

If you haven't read this blog post, you'll want to do that first. It's a quick read and it explains the benefits of freeing yourself from the grips of global, collision-prone CSS class names.

This transformer takes CSS files in, inspects the contained class/id references, renames them uniquely and stores a map of your human-readable names in a simple JSON file.

Here's what you'll want to add to your Cogs config...

cogs.js

module.exports = {
  ...
  pipe: [
    ...
    {
      name: 'local-css',
      only: 'src/my/css/**/*.css',

      // All of the following options are...optional.
      options: {

        // The base directory to store CSS file paths relative to. Default: '.'
        base: "src/my/css",

        // In debug mode, classes will be prepended with their path and
        // human-readable class name. This is highly recommended for development
        // but should be disabled in production. Default: false
        debug: true,

        // The location to store the JSON class name map.
        // Default: class-names.json
        target: "build/my-class-names-map.json",

        // Should not be necessary, but in the case of multiple projects with
        // identical relative CSS file paths being used on the same page, simply
        // insert a unique salt here to break the hash collision. Default: ''
        salt: 'my-unique-salt',

        // The length of the unique class identifier. The higher the number, the
        // lower the chance for a hash collision. Default: 5
        uidLength: 12,

        // How long to wait (in milliseconds) after a change is made before
        // saving the JSON class name map. Default: 500
        debounce: 1000
      }
    }
    ...
  ]
  ...
}

So after this is set up and I run cogs, and assuming I have I'll have a build/my-class-names-map.json file that looks something like...

{
  "one/of/my/css/files": {
    "one-of-my-classes": "abcdef123456",
    "another-class": "zyx123abc456"
  }
}

Now we can load/parse this file with anything that supports JSON (everything) and access the local-css-ified names while references the human-readable class names we want, all without having to sweat global collisions.