theming.mdx

title
Theming

Theming is included in the @emotion/core package.

Add ThemeProvider to the top level of your app and access the theme with props.theme in a styled component or provide a function that accepts the theme as the css prop.

Table of Contents

• Examples
• Usage
• API
  • ThemeProvider
  • withTheme
  • useTheme
• Credits

Examples

css prop

// @live
/** @jsx jsx */
import { jsx, ThemeProvider } from '@emotion/core'

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

render(
  <ThemeProvider theme={theme}>
    <div css={theme => ({ color: theme.colors.primary })}>
      some other text
    </div>
  </ThemeProvider>
)

styled

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

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

const SomeText = styled.div`
  color: ${props => props.theme.colors.primary};
`

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

useTheme hook

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

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>
)

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 * as React from 'react'
import styled from '@emotion/styled'
import { ThemeProvider, withTheme } from '@emotion/core'

// 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 * as PropTypes from 'prop-types'
import * as React from 'react'
import { withTheme } from '@emotion/core'

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, ThemeProvider, useTheme } from '@emotion/core'
import styled from '@emotion/styled'

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.