STYLIS

A Light–weight CSS Preprocessor.

Installation

• Use a Direct Download: <script src=stylis.js></script>
• Use a CDN: <script src=unpkg.com/stylis></script>
• Use NPM: npm install stylis --save

Features

• nesting a { &:hover {} }
• selector namespacing
• vendor prefixing (flex-box, etc...)
• minification
• esm module compatible
• tree-shaking-able

Abstract Syntax Structure

const declaration = {
	value: 'color:red;',
	type: 'decl',
	props: 'color',
	children: 'red',
	line: 1, column: 1
}

const comment = {
	value: '/*@noflip*/',
	type: 'comm',
	props: '/',
	children: '@noflip',
	line: 1, column: 1
}

const ruleset = {
	value: 'h1,h2',
	type: 'rule',
	props: ['h1', 'h2'],
	children: [/* ... */],
	line: 1, column: 1
}

const atruleset = {
	value: '@media (max-width:100), (min-width:100)',
	type: '@media',
	props: ['(max-width:100)', '(min-width:100)'],
	children: [/* ... */],
	line: 1, column: 1
}

Example:

import {compile, serialize, stringify} from 'stylis'

serialize(compile(`h1{all:unset}`), stringify)

Compile

compile('h1{all:unset}') === [{value: 'h1', type: 'rule', props: ['h1'], children: [/* ... */]}]
compile('--foo:unset;') === [{value: '--foo:unset;', type: 'decl', props: '--foo', children: 'unset'}]

Tokenize

tokenize('h1 h2 h3 [h4 h5] fn(args) "a b c"') === ['h1', 'h2', 'h3', '[h4 h5]', 'fn', '(args)', '"a b c"']

Serialize

serialize(compile('h1{all:unset}'), stringify)

Middleware

The middleware helper is a convenient helper utility, that for all intents and purposes you can do without if you intend to implement your own traversal logic. The stringify middleware is one such middleware that can be used in conjunction with it.

Elements passed to middlewares have a root property that is the immediate root/parent of the current element in the compiled output, so it references the parent in the already expanded CSS-like structure. Elements have also parent property that is the immediate parent of the current element from the input structure (structure representing the input string).

Traversal

serialize(compile('h1{all:unset}'), middleware([(element, index, children) => {
	assert(children === element.root.children && children[index] === element.children)
}, stringify])) === 'h1{all:unset;}'

The abstract syntax tree also includes an additional return property for more niche uses.

Prefixing

serialize(compile('h1{all:unset}'), middleware([(element, index, children, callback) => {
	if (element.type === 'decl' && element.props === 'all' && element.children === 'unset')
		element.return = 'color:red;' + element.value
}, stringify])) === 'h1{color:red;all:unset;}'

serialize(compile('h1{all:unset}'), middleware([(element, index, children, callback) => {
	if (element.type === 'rule' && element.props.indexOf('h1') > -1)
		return serialize([{...element, props: ['h2', 'h3']}], callback)
}, stringify])) === 'h2,h3{all:unset;}h1{all:unset;}'

Reading

serialize(compile('h1{all:unset}'), middleware([stringify, (element, index, children) => {
	assert(element.return === 'h1{all:unset;}')
}])) === 'h1{all:unset;color:red;}'

The middlewares in src/Middleware.js dive into tangible examples of how you might implement a middleware, alternatively you could also create your own middleware system as compile returns all the nessessary structure to fork from.

Benchmark

Stylis is at-least 2X faster than its predecesor.

License

Stylis is MIT licensed.