EllieAdam / purifycss

Remove unused CSS. Also works with single-page apps.

PurifyCSS

A function that takes content (HTML/JS/PHP/etc) and CSS, and returns a file made up of only the selectors you use.

PurifyCSS 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](https://github.com/twbs/bootstrap) file: ~140k * App using ~40% of selectors. * Minified: ~117k * Purified + Minified: **~35k**
***

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>;
  );

***

Install

npm install --save purify-css

Require

var purify = require('purify-css');

***

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 source strings + rejected option

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

var options = {
  // Logs out the removed selectors.
  rejected: true
};

purify(content, css, options);

logs out:

.unused-class { display: block; }

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 + minify

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

var options = {
  output: './dist/purified.css',
  
  // Will minify CSS code in addition to purify.
  minify: true
};

purify(content, css, options);

Example with callback

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

purify(content, css, function (purifiedResult) {
  console.log(purifiedResult);
});

Example with callback + options

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

var options = {
  minify: true
};

purify(content, css, options, function (purifiedAndMinifiedResult) {
  console.log(purifiedAndMinifiedResult);
});

***

API in depth

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

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:

• minify: Set to true to minify. Default: false.

• output: Filepath to write purified CSS to. Returns raw string if false. Default: false.

• info: Logs info on how much CSS was removed if true. Default: false.

• rejected: Logs the CSS rules that were removed if true. Default: false.

The (optional) callback argument

Type: Function

A function that will receive the purified CSS as it's argument.

Example of callback use

purify(content, css, options, function(purifiedCSS){
  console.log(purifiedCSS, ' is the result of purify');
});

Example of callback without options

purify(content, css, function(purifiedCSS){
  console.log('callback without options and received', purifiedCSS);
});

***

CLI Usage

$ npm install -g purify-css

$ purifycss
usage: purifycss <css> <content> [option ...]

options:
 --min                Minify CSS
 --out [filepath]     Filepath to write purified CSS to
 --info               Logs info on how much CSS was removed
 --rejected           Logs the CSS rules that were removed

 -h, --help           Prints help (this message) and exits

##### Example CLI Usage

$ purifycss src/js/main.js src/css/main.css src/css/bootstrap.css --min --info --out src/dist/index.css

This will concat both main.css and bootstrap.css and purify it by looking at what CSS selectors were used inside of main.js. It will then write the result to dist/index.css

The --min flag minfies the result.

The --info flag will print this to stdout:

##################################
PurifyCSS has reduced the file size by ~35.2%
##################################

The CLI currently does not support file patterns.

***

Usage at Build Time

Grunt

Gulp

webpack