Awesome

Freyja

A full-featured functional CSS-in-JS solution, adapted from CXS to make it suitable for production websites. You provide a function accepting component props and your application's theme, and returning a map of styles ((theme, props, helpers) => ({key1: style, key2: style})), and useStyles will return a map of classnames (like {key1: className, key2: className}).

Everything CXS has plus:
React hook API
An efficient functional design for complex components
Server-side rendering and client-side hydration
Comprehensive and performant vendor prefixing
Animation keyframes
Ordered media-queries to ensure correct cascade precedence

How to use

Install via npm i freyja.

Create your styled component.

import useStyles from 'freyja'

// this could be in a separate file if you like
const titleStyles = ({font, scale}, {color}, {animation}) => ({
  wrapper: {
    textAlign: 'center',
    padding: scale.large
  },
  title: {
    color,
    fontFamily: font.display,
    animationName: animation({
      from: {
        opacity: 0
      },
      to: {
        opacity: 1
      }
    })
  }
})

const Title = props => {
  const styles = useStyles(titleStyles, props)
  const {text, children} = props
  return (
    <div className={styles.wrapper}>
      <h1 className={styles.title}>{text || children}</h1>
    </div>
  )
}

export default Title

// use like: <Title color={'red'} text={'My first title'} />

Wrap your app in a ThemeProvider (must have only 1 child). Multiple ThemeProviders can be nested, with merged themes only accessible to children within the nested provider:

import {ThemeProvider, animation} from 'freyja'

const theme = {
  font: {
    display: 'Merriweather',
    copy: 'Helvetica'
  },
  scale: {
    small: 12,
    medium: 16,
    large: 24
  },
  animations: {
    spin: animation({ // create named animations with full keyframe support
      from: {
        transform: 'rotate(0deg)'
      },
      to: {
        transform: 'rotate(360deg)'
      }
    })
  }
}

const App = ({children}) => (
  <ThemeProvider theme={theme}>
    <>{children}</>
  </ThemeProvider>
)

export default App

Server-side rendering

Simply call the styleTags dehydration function to receive a string of style tags to insert in your document. Styles will automatically be hydrated on the client.

If rendering your views with React on the server, StyleComponents can be used in the <head>, like: <head><StyleComponents /></head>

import React from 'react'
import {renderToString} from 'react-dom/server'
import {styleTags} from 'freyja'
import App from './App'

const renderMiddleware = (req, res) => {
  const appHTML = renderToString(<App />)
  const appStyleTags = styleTags() // must be called AFTER renderToString()

  res.send(`
    <!doctype html>
    <html>
      <head>
        ${appStyleTags}
      </head>
      <body>
        ${appHTML}
      </body>
    </html>
  `)
}