A CSS-in-JS solution for functional CSS in functional UI components


003.0.5-04 years ago4 years agoMinified + gzip package size for @iwe/cxs in KB



Build Status js-standard-style

Functional CSS for functional UI components

const className = cxs({ color: 'tomato' })

CXS is a functional CSS-in-JS solution that uses atomic styles to maximize deduplication and help with dead code elimination.


  • Three different modes of operation: Atomic, Lite, & Monolithic
  • < 5KB
  • Avoids collisions with atomic rulesets
  • Deduplicates repeated styles
  • Dead-code elimination
  • Framework independent
  • CSS-in-JS
  • Media queries
  • Pseudoclasses
  • Nested selectors
  • Avoid maintaining separate stylesheets
  • Use plain JS objects and types
  • No tagged template literals


npm install cxs


CXS works with any framework, but this example uses React for demonstration purposes.

import React from 'react'
import cxs from 'cxs'

const Box = (props) => {
  return (
    <div {...props} className={className} />

const className = cxs({
  padding: 32,
  backgroundColor: 'tomato'

export default Box


  color: 'tomato',
  ':hover': {
    color: 'red'

Media Queries

  color: 'tomato',
  '@media (min-width: 40em)': {
    color: 'red'

Nested Selectors

  color: 'tomato',
  h1: {
    color: 'red'

Server-Side Rendering

To use CXS in server environments, use the getCss() function to get the static CSS string after rendering a view.

import React from 'react'
import ReactDOMServer from 'react-dom/server'
import cxs from 'cxs'
import App from './App'

const html = ReactDOMServer.renderToString(<App />)
const css = cxs.getCss()

const doc = `<!DOCTYPE html>

// Optionally reset the cache for the next render


CXS offers three different modes of operation, which produce different rules and class names.

import cxsAtomic from 'cxs'
import cxsMonolithic from 'cxs/monolithic'
import cxsLite from 'cxs/lite'

const styles = {
  margin: 0,
  marginBottom: 32,
  padding: 16,
  color: 'tomato',
  ':hover': {
    color: 'orangered'
  '@media (min-width: 40em)': {
    padding: 32

// Each mode returns a different set of class names

// m-0 mb-32 p-16 c-tomato -hover-c-orangered _zsp35u

// _q5nmba

// a b c d e f

Atomic Mode (Default)

import cxs from 'cxs'

The default mode is the atomic mode. This creates atomic rulesets and attempts to create human readable classnames. If a classname is longer than 24 characters, a hashed classname will be used instead.

Lite Mode

import cxs from 'cxs/lite'

For super fast performance, use the cxs/lite module. Lite mode creates alphabetic class names in a sequential order and does not support nested selectors.

Since the class names in cxs/lite are not created in a functional manner, when using cxs/lite on both the server and client, the styles will need to be rehydrated.

// Server
const css = cxs.getCss()

const html = `<!DOCTYPE html>
<style id='cxs-style'>${css}</style>
// Client
import cxs from 'cxs/lite'

const styleTag = document.getElementById('cxs-style')
const serverCss = styleTag.innerHTML


Monolithic Mode

import cxs from 'cxs/monolithic'

To create encapsulated monolithic styles with CXS and use single hashed class names, import the monolithic module.

The monolithic module also accepts custom selectors for styling things like the body element.

cxs('body', {
  fontFamily: '-apple-system, sans-serif',
  margin: 0,
  lineHeight: 1.5


import cxs from 'cxs'

// Creates styles and returns micro classnames
cxs({ color: 'tomato' })

// Returns a CSS string of attached rules. Useful for server-side rendering

// Clear the cache and flush the glamor stylesheet.
// This is useful for cleaning up in server-side contexts.

Additional exports

import {
  // The threepointone/glamor StyleSheet instance
  // See https://github.com/threepointone/glamor
  // Same as cxs.getCss
  // Same as cxs.reset
} from 'cxs'

Vendor prefixes

CXS does not handle vendor prefixing to keep the module size at a minimum. To add vendor prefixes, use a prefixing module like inline-style-prefixer

import cxs from 'cxs'
import prefixer from 'inline-style-prefixer/static'

const prefixed = prefixer({
  display: 'flex'
const cx = cxs(prefixed)

Browser support

IE9+, due to the following:

  • Array.filter
  • Array.map
  • Array.forEach


MIT License

If you find any bugs or have a feature request, please open an issue on github!

The npm package download data comes from npm's download counts api and package details come from npms.io.