createComponent

Note: If you're working with React > 16.3, we highly recommend using the useFela hook instead.
It's more easy and safe to use and also has the best rendering performance. A HoC (Higher-order Component(new tab)) that creates a presentational React component using the rendered 

rule
as className.

It automatically composes rules and passed props for nested Fela components.

Arguments

ArgumentTypeDefaultDescription
ruleFunction
Object		Either a style object or rule function which satisfies the rule behavior and returns a valid style object.
typestring?
Component(new tab)?
div
Component or HTML element which is used as the render base element.
Note: If a Component is passed, then it receives a className property.
passThroughPropsArray?
Function?		A list of props that get passed to the underlying element.
Alternatively a function of 
props
that returns an array of prop names.

Returns

(Function): Stateless functional component.

Imports

import { createComponent } from 'react-fela'
import { createComponent } from 'preact-fela'
import { createComponent } from 'inferno-fela'

Example

Header.js

const title = ({ small, fontSize, color }) => ({
  lineHeight: small ? 1.2 : 1.5,
  fontSize: fontSize + 'px',
  color: color
})
const Title = createComponent(title, 'div', [ 'onClick' ])
const Usage = <Title fontSize={23} color="red" onClick={...}>Hello World</Title>
// <div className="a b c" onclick="...">Hello World</div>

Passing Props

Using the 

passThroughProps
parameter allows us to pass props to the underlying DOM element. This is helpful if you want to pass e.g. events such as 
onClick
. There are some props that are automatically passed and thus do not need to be specified explicitly:

  • className
  • style
  • id

If passing a className, it will automatically be concatenated with the Fela generated className. This allows composing multiple Fela Components.

Functional passThroughProps

You may also pass a function of 

props
as 
passThroughProps
. It must return an array of prop names. e.g. to pass all props you can do:

Title.js

const Title = createComponent(title, 'div', (props) => Object.keys(props))
// shorthand
const Title = createComponent(title, 'div', Object.keys)

Note: The same can be achieved via createComponentWithProxy.

Dynamically passing Props

This use case is especially important for library owners. Instead of passing the 

passThroughProps
to the 
createComponent
call directly, one can also use the 
passThrough
prop on the created component to achieve the same effect.

Title.js

const title = () => ({
  color: 'red'
})
const Title = createComponent(title)
const Usage = <Title onClick={...} passThrough={[ 'onClick' ]}>Hello World</Title>
// => <div className="a" onclick="...">Hello World</div>

Extending Styles

It's possible to extend component styles with an 

extend
prop that can be either an object or a function.

Title.js

const title = () => ({
  color: 'red'
})
const Title = createComponent(title)
const Usage = <Title extend={{ color: 'blue' }}>Hello World</Title>,
// => <div className="a">Hello World</div>
// => .a { color: blue }
const extendTitle = props => ({
  color: props.color
})
const ExtendedTitle = <Title extend={extendTitle} color="green">Hello World</Title>
// => <div className="a">Hello World</div>
// => .a { color: green }

Custom Type on Runtime

To change the 

type
on runtime and/or for each component, you may use the 
as
prop.

Title.js

const title = (props) => ({
  color: 'red',
})
const Title = createComponent(title)
const Usage = <Title as="h1">Hello World</Title>
// => <h1 className="a">Hello World</h1>

Static Style Object

Instead of rendering a props-depending rule, we can also use plain objects to render static style objects.

Title.js

const style = {
  fontSize: '15px',
  color: 'red',
}
const Title = createComponent(style, 'h1')
const Usage = <Title>Hello World</Title>
// => <h1 className="a b">Hello World</h1>