Usage with React

Fela was always designed with React in mind, but is not bound to React by default. If you want to use it with React, you should also install the official React bindings for Fela.

npm i --save react-fela

Presentational Components

While not required, we highly recommend to split your components into presentational and container components. Where container components manage the application logic, presentational components should only describe how your application is displayed (markup & styling). They get data passed as props and return a representation of your view for those props. If we strictly separate our components, we actually only use Fela for presentational components.

Presentational Components from Rules

From the very beginning, react-fela ships the createComponent API. It basically creates primitive React components using the passed rule to style it. This works as easy as e.g. styled-components.

import { createComponent } from 'react-fela'

const container = ({ padding }) => ({
  padding: padding + 'px',
  backgroundColor: 'rgb(124, 114, 231)',
  fontSize: '20px'
})

const Container = createComponent(container)

// <div class="a b c">Padding everywhere</div>
<Container padding={20}>Padding everywhere</Container>

Custom element/component

createComponent renders into a div by default, but is also able to render into any other HTML element or React component.
Simply pass either a string (HTML element) or function/class (React component) as a second argument.

import { createComponent } from 'react-fela'

const title = ({ fontSize, color }) => ({
  fontSize: fontSize + 'px',
  color: color
})

const Title = createComponent(title, 'h1')

// <h1 class="a b">I am red</h1>
<Title fontSize={20} color="red">I am red</Title>

Composition

It also supports automatic style composition for multiple composed Fela components.

import { createComponent } from 'react-fela'

const title = ({ color }) => ({
  fontSize: '20px',
  color: color
})

const bordered = ({ borderWidth }) => ({
  border: `${borderWidth}px solid green`
})

const Title = createComponent(title, 'h1')
const BorderedTitle = createComponent(bordered, Title)

// <h1 class="a b c">I am red and bordered</h1>
<BorderedTitle color='red' borderWidth={2}>I am red and bordered</BorderedTitle>

For advanced API documentation, please check out the createComponent API docs.
Amongst other things, you can learn how to pass props to the underlying element.

Component Theming

For flexible and yet simple component theming, react-fela ships the <ThemeProvider> component. It leverages React's context to pass the theme to all child elements.

The theme can then be accessed via props.theme within createComponent.

import { createComponent, ThemeProvider } from 'react-fela'


const theme = {
  fontColor: 'green',
  fontSize: '30px'
}

const title = props => ({
  fontSize: props.theme.fontSize,
  color: props.theme.fontColor
})

const Title = createComponent(title, 'h1')

// <h1 class="a b"></h1>
<ThemeProvider theme={theme}>
  <Title>I am green and big</Title>
</ThemeProvider>

You may also nest multiple <ThemeProvider>. The theme object will then automatically get merged to extend the previous theme. To force overwrite the theme (without merging) you may pass a overwrite prop.

Passing the Renderer

We like to avoid using a global Fela renderer which is why the React bindings ship with a <Provider> component. It takes our renderer and uses React's context to pass it down the whole component tree.

import { createRenderer } from 'fela'
import { Provider } from 'react-fela'
import { render } from 'react-dom'
import React from 'react'

const renderer = createRenderer()

render(
  <Provider renderer={renderer}>
    <App />
  </Provider>,
  document.getElementById('app')
)

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