emotion-theming

emotion-theming

A CSS-in-JS theming solution for React

emotion-theming is a theming library inspired by styled-components

Table of Contents

• Install
• Usage
• API
  • ThemeProvider
  • withTheme
  • useTheme
• Credits
• License

Install

# add --save if using npm@4 or lower
npm i emotion-theming

# or
yarn add emotion-theming

Usage

Theming is accomplished by placing the ThemeProvider component, at the top of the React component tree and wrapping descendants with the withTheme higher-order component. This HOC gets the current theme and injects it as a "prop" into your own component.

The theme prop is automatically injected into components created with styled. The theme can also be accessed via passing a function to the css prop.

// Page.js
import * as React from 'react'
/** @jsx jsx */
import { jsx } from '@emotion/core'
import styled from '@emotion/styled'

const Container = styled.div({
  background: 'whitesmoke',
  height: '100vh'
})

const Headline = styled.h1`
  color: ${props => props.theme.color};
  font-family: sans-serif;
`

export default class Page extends React.Component {
  render() {
    return (
      <Container>
        <Headline>I'm red!</Headline>
        <p css={theme => ({ color: theme.color })}>I'm also red!</p>
      </Container>
    )
  }
}

// App.js
import React from 'react'
import ReactDOM from 'react-dom'
import { ThemeProvider } from 'emotion-theming'

import Page from './Page.js'

const theme = {
  color: 'red'
}

class App extends React.Component {
  render() {
    return (
      <ThemeProvider theme={theme}>
        <Page />
      </ThemeProvider>
    )
  }
}

API

ThemeProvider: React.ComponentType

A React component that passes the theme object down the component tree via context. Additional ThemeProvider components can be added deeper in the tree to override the original theme. The theme object will be merged into its ancestor as if by Object.assign. If a function is passed instead of an object it will be called with the ancestor theme and the result will be the new theme.

Accepts:

• children: React.Node
• theme: Object|Object => Object - An object or function that provides an object.

import React from 'react'
import styled from '@emotion/styled'
import { ThemeProvider, withTheme } from 'emotion-theming'

// object-style theme

const theme = {
  backgroundColor: 'green',
  color: 'red'
}

// function-style theme; note that if multiple <ThemeProvider> are used,
// the parent theme will be passed as a function argument

const adjustedTheme = ancestorTheme => ({ ...ancestorTheme, color: 'blue' })

class Container extends React.Component {
  render() {
    return (
      <ThemeProvider theme={theme}>
        <ThemeProvider theme={adjustedTheme}>
          <Text>Boom shaka laka!</Text>
        </ThemeProvider>
      </ThemeProvider>
    )
  }
}

Note:

Make sure to hoist your theme out of render otherwise you may have performance problems.

withTheme(component: React.ComponentType): React.ComponentType

A higher-order component that provides the current theme as a prop to the wrapped child and listens for changes. If the theme is updated, the child component will be re-rendered accordingly.

import PropTypes from 'prop-types'
import React from 'react'
import { withTheme } from 'emotion-theming'

class TellMeTheColor extends React.Component {
  render() {
    return <div>The color is {this.props.theme.color}.</div>
  }
}

TellMeTheColor.propTypes = {
  theme: PropTypes.shape({
    color: PropTypes.string
  })
}

const TellMeTheColorWithTheme = withTheme(TellMeTheColor)

useTheme

A React hook that provides the current theme as its value. If the theme is updated, the child component will be re-rendered accordingly.

// @live
/** @jsx jsx */
import { jsx } from '@emotion/core'
import styled from '@emotion/styled'
import { ThemeProvider, useTheme } from 'emotion-theming'

const theme = {
  colors: {
    primary: 'hotpink'
  }
}

function SomeText (props) {
  const theme = useTheme()
  return (
    <div
      css={{ color: theme.colors.primary }}
      {...props}
    />
  )
}

render(
  <ThemeProvider theme={theme}>
    <SomeText>some text</SomeText>
  </ThemeProvider>
)

Credits

Thanks goes to the styled-components team and their contributors who designed this API.

License

MIT 2017-present