Fela is a small, high-performant and framework-agnostic toolbelt to handle state-driven styling in JavaScript.

It is dynamic by design and renders your styles depending on your application state.

It generates atomic CSS and supports all common CSS features such as media queries, pseudo classes, keyframes and font-faces. Fela ships with a powerful plugin API adding e.g. vendor prefixing or fallback value support.

Fela can be used with React or with any other view library. It even supports React Native.

Support Us

Support Robin Weser's work on Fela and its ecosystem directly via GitHub Sponsors.

Benefits

- Predictable Styling
- Scoped Atomic CSS
- Minimal Bundle Size
- No Specificity Issues
- No Naming Conflicts
- Framework-Agnostic
- Huge Ecosystem
- RTL Support

> Read more about the benefits!

The Gist

Fela's core principle is to consider style as a function of state.

The whole API and all plugins and bindings are built on that idea.

It is reactive and auto-updates once registered to the DOM.


The following example illustrates the key parts of Fela though it only shows the very basics.

``javascript
import { createRenderer } from 'fela'

// a simple style rule is a pure function of state
// that returns an object of style declarations
const rule = (state) => ({
textAlign: 'center',
padding: '5px 10px',
// directly use the state to compute style values
fontSize: state.fontSize + 'pt',
borderRadius: 5,
// deeply nest media queries and pseudo classes
':hover': {
fontSize: state.fontSize + 2 + 'pt',
boxShadow: '0 0 2px rgb(70, 70, 70)',
},
})

const renderer = createRenderer()

// fela generates atomic CSS classes in order to achieve
// maximal style reuse and minimal CSS output
const className = renderer.renderRule(rule, {
fontSize: 14,
}) // => a b c d e f
`

The generated CSS output would look like this:

`CSS
.a { text-align: center }
.b { padding: 5px 10px }
.c { font-size: 14pt }
.d { border-radius: 5px }
.e:hover { font-size: 16pt }
.f:hover { box-shadow: 0 0 2px rgb(70, 70, 70) }
`

$3

If you're using Fela, you're most likely also using React.

Using the React bindings, you get powerful APIs to create primitive components.


> Read: Usage with React for a full guide.

`jsx
import * as React from 'react'
import { useFela } from 'react-fela'

const rule = ({ fontSize }) => ({
textAlign: 'center',
padding: '5px 10px',
// directly use the props to compute style values
fontSize: fontSize + 'pt',
borderRadius: 5,
':hover': {
fontSize: fontSize + 2 + 'pt',
boxShadow: '0 0 2px rgb(70, 70, 70)',
},
})

function Button({ fontSize, children }) {
const { css } = useFela({ fontSize })

return {children}
}
`

> Check this example on CodeSandbox

Examples

- Fela + React (source)
- React Styleguidist (source)
- React Native (source)
- ReasonReact
- Next
- Fela + Preact (source)
- Fela + Inferno (source)
- Fela + HyperScript
- Fela + Cycle
- Fela + Next.js

Documentation

- Getting Started
- Ecosystem
- Migration Guide
- Changelog
- FAQ

Workshop

If you are coming from CSS and want to learn JavaScript Styling with Fela, there is a full-feature fela-workshop which demonstrates typical Fela use cases. It teaches all important parts, step by step with simple examples. If you already know other CSS in JS solutions and are just switching to Fela, you might not need to do the whole workshop, but it still provides useful information to get started quickly.

Talks

- CSS in JS: The Good & Bad Parts (Slides)
- _by Robin Weser_
- CSS in JS: Patterns
- _by Vojtech Miksu_

Posts

- Style as a Function of State
- _by Robin Weser_
- CSS in JS: The Argument Refined
- _by Daniel Steigerwald_
- What is Fela?
- _by David Sinclair_
- Choosing a CSS in JS library
- _by Thomas Roch_
- Introducing Fela 6.0
- _by Robin Weser_
- A journey into CSS and then into CSS-in-JS
- _by Prithvi Raju_
- CSS In JS — Future of styling components
- _by Manjula Dube_
- Styling Components with React Fela
- _by Josh Sherman_
- The Future of Fela
- _by Robin Weser_

Ecosystem

There are tons of useful packages maintained within this repository including plugins, enhancers, bindings and tools that can be used together with Fela. Check the Ecosystem documentation for a quick overview.

Community

Apart from all the packages managed within this repository, there are many community third-party projects that are worth mentioning:

- aesthetic - React style and theme layer with Fela support
- base-styling-components - Abstract Box and Text Components
- bs-react-fela - BuckleScript / ReasonReact bindings for Fela
- catstack - A modular mad science framework for teams working on production web apps
- css-in-js-playground - A simple playground for CSS in JS solutions
- cf-ui - Cloudflare UI Framework
- counter-component-with-react-mobx-fela - Counter Component using Fela
- cycle-fela - Cycle bindings for Fela
- dogstack - A popular-choice grab-bag framework for teams working on production web apps
- fela-components - Styling library for React and Fela
- fela-react-helpers - A set of useful helpers for Fela
- fela-react-prop - Generate class names for fela style rule and apply them as property on a wrapped component
- fela-styles-connector - Simplified react-fela connect` with auto-bound styles
- frejya: Pass styles as props to components
- gatsby-plugin-fela - Integrates fela with Gatsby
- hyper-fela - HyperScript bindings for Fela
- htz-frontend - Source for Haaretz frontend app(s)
- kilvin - Primitive React Layout Components with Fela
- olymp - Create and build a next gen app using node, react, cssInJS and other cool stuff
- preact-fela-simple - Super simple Preact bindings for Fela
- reason-react-starter - A ReasonReact starter kit using Fela
- storybook-addon-props-fela: Document the props of your Fela components in storybook.
- superslider - Slider Component using Fela
- telaviv - React Universal Rendering
- vashet - ClojureScript wrapper for Fela
- veel - Base react styling components using fela with a design system
- vue-fela - Vue bindings for Fela
- black-box - combines behavior, presentation, structure in one place & creates all-in-one components using only JS syntax

Support

Got a question? Come and join us on Spectrum!

We'd love to help out. We also highly appreciate any feedback.

Don't want to miss any update? Follow us on Twitter.

Who's using Fela?

> Your company is using Fela, but is not listed yet? Add your company / organisation

- abilis
- Bookmyshow
- BdP LV RPS
- Cloudflare
- dm-drogerie markt
- dmTECH
- Espressive
- Gazzer
- HelloFresh
- Indoqa
- Kilix
- Lusk
- MediaFire
- Medium
- Microsoft
- N26
- Net-A-Porter
- NinjaConcept
- Optisure
- Robin Weser
- Rocket Station
- Root Systems
- Space Between
- V2
- Volvo Cars
- Zendesk

Contributing

This project exists thanks to all the people who contribute.

We highly appreciate any contribution.

For more information follow the contribution guide.

Also, please read our code of conduct.

License

Fela is licensed under the MIT License.

Documentation is licensed under Creative Commons License.

Created with ♥ by @robinweser and all the great contributors.