Renderer Configuration

We already learned that the renderer is configurable with e.g. plugins, but there are some more options.

In general, our renderer accepts a config object. The following table shows each configuration option, its expected value, its default value and what it is used for.

We might introduce more configuration options with future releases, so be sure to frequently check for updates.

OptionValueDefaultDescription
plugins(Array?)A list of plugins to process styles before rendering
keyframePrefixes(Array?)
['-webkit-', '-moz-']
A list of which additional 
@keyframes
prefixes are rendered
enhancers(Array?)A list of enhancers to enhance the renderer
mediaQueryOrder(Array?)An explicit order in which 
@media
queries are rendered
sortMediaQueryFunctionA function with the same signature as sort functions in e.g. 
Array.prototype.sort
for dynamically sorting media queries. Maps over an array of media query strings. Overwrites 
mediaQueryOrder
.
selectorPrefix(string?)Prepend a static prefix to every generated class and keyframe. It must only consist of 
a-zA-Z0-9-_
and start with 
a-zA-Z_
.
specificityPrefix(string?)Prepend a static prefix to every CSS selector. It must only consist of 
a-zA-Z0-9-_
and start with 
a-zA-Z_
.
styleNodeAttributes(Object?)A map of attributes that's passed to the generated style nodes.
filterClassName(Function?)
cls => cls.indexOf('ad') !== -1
Filter-function to filter used class names
devMode(Boolean?)
false
Enabling development mode for better developer experience. Make sure to disable devMode in production.
propertyPriority(Object?)A map of property-priority pairs where default priority is 
1
. Use numbers starting with 
2
to prioritize certain properties over others.

Feature Flags

Additionally to the above mentioned options, we can also pass feature flags to enable experimental features.

Note: Those are experimental features and do not adhere to semantic versioning. Use at your own risk!

OptionDescription
optimizeCaching Enables improved caching mechanism to speed up rendering.

Example

import { createRenderer } from 'fela'
import prefixer from 'fela-plugin-prefixer'
import unit from 'fela-plugin-unit'
import fallbackValue from 'fela-plugin-fallback-value'
import beautifier from 'fela-beautifier'
import { renderToString } from 'fela-dom'
const config = {
  devMode: process.env.NODE_ENV !== 'production',
  plugins: [unit('em'), prefixer(), fallbackValue()],
  keyframePrefixes: ['-webkit-'],
  enhancers: [beautifier()],
  mediaQueryOrder: ['(min-height: 300px)', '(min-height: 500px)'],
  selectorPrefix: 'fela_',
  specificityPrefix: '.App ',
  styleNodeAttributes: {
    nonce: 'XXX',
  },
  // feature flags
  optimizeCaching: true,
}
const renderer = createRenderer(config)
const keyframe = (props) => ({
  from: {
    width: 'calc(100% - 50px)',
    height: props.height * 2,
  },
  to: {
    width: 'calc(50% - 50px)',
    height: props.height,
  },
})
const rule = (props) => ({
  color: props.color,
  fontSize: 12,
})
renderer.renderRule(rule, { color: 'red ' })
renderer.renderKeyframe(keyframe, { height: 100 })
console.log(renderToString(renderer))

Rendered CSS

@-webkit-keyframes fela_k1 {
  from {
    width: -webkit-calc(100% - 50px);
    width: -moz-calc(100% - 50px);
    width: calc(100% - 50px);
    height: 200em;
  }
  to {
    width: -webkit-calc(50% - 50px);
    width: -moz-calc(50% - 50px);
    width: calc(50% - 50px);
    height: 100em;
  }
}
@keyframes fela_k1 {
  from {
    width: -webkit-calc(100% - 50px);
    width: -moz-calc(100% - 50px);
    width: calc(100% - 50px);
    height: 200em;
  }
  to {
    width: -webkit-calc(50% - 50px);
    width: -moz-calc(50% - 50px);
    width: calc(50% - 50px);
    height: 100em;
  }
}
.App .fela_a {
  color: red;
}
.App .fela_b {
  font-size: 12px;
}