Micro-Purify

This is a zero-dependencies fork of purify-css.

Micro-purify is a function that takes content (HTML/JS/PHP/etc) and CSS, and returns only the used CSS. Micro-Purify does not modify the original CSS files. You can write to a new file, like minification.
If your application is using a CSS framework, this is especially useful as many selectors are often unused.

Potential reduction

• Bootstrap file: ~140k
• App using ~40% of selectors.
• Minified: ~117k
• Purified + Minified: ~35k

Usage

Standalone

Installation

npm i -D micro-purify

import purify from "micro-purify"
const purify = require("micro-purify")

let content = ""
let css = ""
let options = {
    output: "filepath/output.css"
}
purify(content, css, options)

How it works

Used selector detection

Statically analyzes your code to pick up which selectors are used.
But will it catch all of the cases?

Let's start off simple.

Detecting the use of: button-active

  <!-- html -->
  <!-- class directly on element -->
  <div class="button-active">click</div>

  // javascript
  // Anytime your class name is together in your files, it will find it.
  $(button).addClass('button-active');

Now let's get crazy.

Detecting the use of: button-active

  // Can detect if class is split.
  var half = 'button-';
  $(button).addClass(half + 'active');

  // Can detect if class is joined.
  var dynamicClass = ['button', 'active'].join('-');
  $(button).addClass(dynamicClass);

  // Can detect various more ways, including all Javascript frameworks.
  // A React example.
  var classes = classNames({
    'button-active': this.state.buttonActive
  });

  return (
    <button className={classes}>Submit</button>;
  );

Examples

Example with source strings

var content = '<button class="button-active"> Login </button>';
var css = '.button-active { color: green; }   .unused-class { display: block; }';

console.log(purify(content, css));

logs out:

.button-active { color: green; }

Example with glob file patterns + writing to a file

var content = ['**/src/js/*.js', '**/src/html/*.html'];
var css = ['**/src/css/*.css'];

var options = {
  // Will write purified CSS to this file.
  output: './dist/purified.css'
};

purify(content, css, options);

Example with both glob file patterns and source strings

var content = ['**/src/js/*.js', '**/src/html/*.html'];
var css = '.button-active { color: green; } .unused-class { display: block; }';

var options = {
  output: './dist/purified.css'
};

purify(content, css, options);

API in depth

// Three possible arguments.
purify(content, css, options);

The content argument

Type: Array or String

Array of glob file patterns to the files to search through for used classes (HTML, JS, PHP, ERB, Templates, anything that uses CSS selectors).

String of content to look at for used classes.

The css argument

Type: Array or String

Array of glob file patterns to the CSS files you want to filter.

String of CSS to purify.

The (optional) options argument

Type: Object

Properties of options object:

• whitelist Array of selectors to always leave in. Ex. ['button-active', '*modal*'] this will leave any selector that includes modal in it and selectors that match button-active. (wrapping the string with *'s, leaves all selectors that include it)