PreCSS

PreCSS is a tool that allows you to use Sass-like markup in your CSS files.

Enjoy a familiar syntax with variables, mixins, conditionals, and other goodies.

Variables

/* before */

$blue: #056ef0;
$column: 200px;

.menu {
	width: calc(4 * $column);
}

.menu_link {
	background: $blue;
	width: $column;
}

/* after */

.menu {
	width: calc(4 * 200px);
}

.menu_link {
	background: #056ef0;
	width: 200px;
}

Conditionals

/* before */

.notice--clear {
	@if 3 < 5 {
		background: green;
	}
	@else {
		background: blue;
	}
}

/* after */

.notice--clear {
	background: green;
}

Loops

/* before */

@for $i from 1 to 3 {
	.b-$i { width: $(i)px; }
}

/* after */

.b-1 {
	width: 1px
}
.b-2 {
	width: 2px
}
.b-3 {
	width: 3px
}

/* before */

@each $icon in (foo, bar, baz) {
	.icon-$(icon) {
		background: url('icons/$(icon).png');
	}
}

/* after */

.icon-foo {
	background: url('icons/foo.png');
}

.icon-bar {
	background: url('icons/bar.png');
}

.icon-baz {
	background: url('icons/baz.png');
}

Mixins

/* before */

@define-mixin icon $name {
	padding-left: 16px;

	&::after {
		content: "";
		background-image: url(/icons/$(name).png);
	}
}

.search {
	@mixin icon search;
}

/* after */

.search {
	padding-left: 16px;
}

.search::after {
	content: "";
	background-image: url(/icons/search.png);
}

Extends

/* before */

@define-extend bg-green {
	background: green;
}

.notice--clear {
	@extend bg-green;
}

/* after */

.notice--clear {
	background: green;
}

Imports

/* Before */

@import "partials/base"; /* Contents of partials/_base.css: `body { background: black; }` */


/* After */

body { background: black; }

Property Lookup

/* Before */

.heading {
	margin: 20px;
	padding: @margin;
}

/* After */

.heading {
	margin: 20px;
	padding: 20px;
}

Root

/* Before */

.parent {
	background: white;

	@at-root{
		.child {
			background: black;
		}
	}
}

/* After */

.child {
	background: black;
}

.parent {
	background: white;
}

Usage

Follow these simple steps to use PreCSS.

Add PreCSS to your build tool:

npm install precss --save-dev

Add the PostCSS SCSS parser to your build tool:

npm install postcss-scss --save-dev

Node

require('precss')({ /* options */ }).process(YOUR_CSS, { parser: require('postcss-scss') });

PostCSS

Add PostCSS to your build tool:

npm install postcss --save-dev

Load PreCSS as a PostCSS plugin:

postcss([
    require('precss')({ /* options */ })
]).process(YOUR_CSS, { parser: require('postcss-scss') }).then(function (result) {
	// do something with result.css
});

Gulp

Add Gulp PostCSS to your build tool:

npm install gulp-postcss --save-dev

Enable PreCSS within your Gulpfile:

var postcss = require('gulp-postcss');

gulp.task('css', function () {
    return gulp.src('./css/src/*.css').pipe(
        postcss([
            require('precss')({ /* options */ })
        ])
    ).pipe(
        gulp.dest('./css')
    );
});

Grunt

Add Grunt PostCSS to your build tool:

npm install precss --save-dev

Enable PreCSS within your Gruntfile:

grunt.loadNpmTasks('grunt-postcss');

grunt.initConfig({
	postcss: {
		options: {
			parser: require('postcss-scss'),
			processors: [
				require('precss')({ /* options */ })
			]
		},
		dist: {
			src: 'css/*.css'
		}
	}
});

Plugins

PreCSS blends Sass-like strength with W3C future-syntax superpower, powered by the following plugins (in this order):

• postcss-partial-import: W3C and Sass-like imports
• postcss-mixins: Sass-like mixins
• postcss-advanced-variables: Sass-like variables and methods
• postcss-custom-selectors: W3C custom selectors
• postcss-custom-media: W3C custom media queries
• postcss-custom-properties: W3C custom variables
• postcss-media-minmax: W3C < <= >= > media queries
• postcss-color-function: W3C color methods
• postcss-nesting: W3C nested selectors
• postcss-nested: Sass-like nested selectors
• postcss-atroot: place rules back up to the root
• postcss-property-lookup: reference other property values
• postcss-extend: W3C and Sass-like extend methods
• postcss-selector-matches: W3C multiple matches pseudo-classes
• postcss-selector-not: W3C multiple not pseudo-classes