• Features
• Installation
• How it Works
• Examples
  • CSS Function
  • CSS Prop
  • Styled Function
  • Box Component
  • Psuedoclasses
  • Media Queries
  • Child Selectors
• Acknowledgments
• Development

• Zero-runtime CSS in JS when statically rendered
• Generates atomic class names
• Deduplicates styles across environments
• Works in Server and Client Components
• Compatible with Suspense and streaming
• Encourages encapsulation
• Supports css prop with JSX pragma
• Loads styles on demand
• Allows shipping CSS in NPM packages
• 2.16kb minified and gzipped

npm install restyle

import { styled } from 'restyle'

export const Box = styled('div', {
  padding: '1rem',
  backgroundColor: 'peachpuff',
})

Restyle leverages React's new ability to hoist style elements by generating atomic CSS on-demand to provide a flexible and efficient styling solution for React components. Here's a high-level overview of how it operates:

1. Styles Parsing: Restyle takes a styles object of CSS and parses it, generating atomic class names for each unique style property and value pair:

import { css } from 'restyle'

const [classNames, styleElement] = css({
  padding: '1rem',
  backgroundColor: 'peachpuff',
})

// classNames: 'x1y2 x3z4'
// styleElement: <style>.x1y2{padding:1rem}.x3z4{background-color:peachpuff}</style>

2. Class Names Generation and Deduplication: Atomic class names are generated using a hashing function to ensure uniqueness and prevent collisions. Class names are cached per request, optimizing performance and reducing the overall size of the generated CSS:

import { css } from 'restyle'

const [classNames] = css({
  padding: '1rem',
  backgroundColor: 'tomato',
})

// Example output: 'x1y2 xfg3'

3. Atomic CSS: By breaking down styles into atomic units, it allows for highly reusable class names, making it easy to manage and override styles while reducing the overall size of the CSS produced:

import { css } from 'restyle'

const styles = {
  padding: '1rem',
  backgroundColor: 'rebeccapurple',
}

const [classNames, styleElement] = css(styles)

// classNames: 'x1y2 x4z1'
// Reuse class names for other elements
const buttonStyles = {
  ...styles,
  border: '1px solid black',
}

const [buttonClassNames, buttonStyleElement] = css(buttonStyles)

// buttonClassNames: 'x1y2 x4z1 x5a6'

4. On-Demand Style Injection: Styles are only added to the DOM when the component or element is rendered:

import { css } from 'restyle'

export default function OnDemandStyles() {
  const [classNames, styleElement] = css({
    padding: '1rem',
    backgroundColor: 'papayawhip',
  })

  return (
    <>
      <div className={classNames}>Hello World</div>
      {styleElement}
    </>
  )
}

5. Integration with JSX Pragma: Easily add support for the css prop via the JSX pragma, allowing colocated inline CSS styles directly on JSX elements.

/** @jsxImportSource restyle */

export default function MyComponent() {
  return (
    <div
      css={{
        padding: '1rem',
        backgroundColor: 'peachpuff',
      }}
    >
      Hello World
    </div>
  )
}

• CSS Function
• CSS Prop
• Styled Function
• Box Component
• Psuedoclasses
• Media Queries
• Child Selectors

The css function returns a tuple of class names and the style tags to render. You can use the class names to apply styles to an element and the style tag to inject the styles into the head of the document:

import React from 'react'
import { css } from 'restyle'

export default function BasicUsage() {
  const [classNames, styles] = css({
    padding: '1rem',
    backgroundColor: 'peachpuff',
  })

  return (
    <>
      <div className={classNames}>Hello World</div>
      {styles}
    </>
  )
}

The css function is most useful for components. However, you can use the css prop to style elements directly. The pragma will take care of applying the class names and injecting the style tag.

First, configure the pragma in your tsconfig.json file:

{
  "compilerOptions": {
    "jsxImportSource": "restyle"
  }
}

Now, you can use the css prop to style elements:

export default function CSSProp() {
  return (
    <div
      css={{
        padding: '1rem',
        backgroundColor: 'peachpuff',
      }}
    >
      Hello World
    </div>
  )
}

Alternatively, you can set the pragma at the top of the file:

/** @jsxImportSource restyle */

export default function CSSProp() {
  return (
    <div
      css={{
        padding: '1rem',
        backgroundColor: 'peachpuff',
      }}
    >
      Hello World
    </div>
  )
}

The styled function is a higher-order function that takes an HTML element tag name or a component that accepts a className prop and a initial styles object that returns a styled component that can accept a css prop:

import Link from 'next/link'
import { styled } from 'restyle'

const StyleLink = styled(Link, {
  color: 'rebeccapurple',
  textDecoration: 'none',
})

import React from 'react'
import { css } from 'restyle'

export function Box({
  children,
  display = 'flex',
  alignItems,
  justifyContent,
  padding,
  backgroundColor,
}) {
  const [classNames, styles] = css({
    display,
    alignItems,
    justifyContent,
    padding,
    backgroundColor,
  })
  return (
    <div className={classNames}>
      {children}
      {styles}
    </div>
  )
}

/** @jsxImportSource restyle */

export default function Hover() {
  return (
    <div
      css={{
        ':hover': {
          opacity: 0.8,
        },
      }}
    >
      Hover me
    </div>
  )
}

/** @jsxImportSource restyle */

export default function MediaQueries() {
  return (
    <h1
      css={{
        fontSize: '2rem',
        '@media screen and (min-width: 40em)': {
          fontSize: '3.5rem',
        },
      }}
    >
      Resize the window
    </h1>
  )
}

/** @jsxImportSource restyle */

export default function ChildSelectors() {
  return (
    <div
      css={{
        color: 'black',
        '> a': {
          color: 'tomato',
        },
      }}
    >
      Parent
      <a href="#">Link</a>
    </div>
  )
}

This project is inspired by and builds upon the ideas and work of several other projects in the CSS-in-JS ecosystem:

• The React team for the style hoisting feature which makes this library possible
• Glamor for introducing the css prop
• Styled-Components for introducing the styled function
• Emotion for types and the modern JSX pragma
• CXS for atomic CSS generation
• Fela for their approach to deterministic atomic class name ordering

Thank you to WebReflection for the restyle NPM package name.

In one terminal, run the following command to build the library and watch for changes:

npm install
npm run dev

In another terminal, run the following command to start the development server for the site:

cd site
npm install
npm run dev