css-to-react-native

Converts CSS text to a React Native stylesheet object.

Try it here

font-size: 18px;
line-height: 24px;
color: red;

{
  fontSize: 18,
  lineHeight: 24,
  color: 'red',
}

Converts all number-like values to numbers, and string-like to strings.

Automatically converts indirect values to their React Native equivalents.

text-shadow-offset: 10px 5px;
font-variant: small-caps;
transform: translate(10px, 5px) scale(5);

{
  textShadowOffset: { width: 10, height: 5 },
  fontVariant: ['small-caps'],
  // Fixes backwards transform order
  transform: [
    { translateY: 5 },
    { translateX: 10 },
    { scale: 5 },
  ]
}

Also allows shorthand values.

font: bold 14px/16px "Helvetica";
margin: 5px 7px 2px;

{
  fontFamily: 'Helvetica',
  fontSize: 14,
  fontWeight: 'bold',
  fontStyle: 'normal',
  fontVariant: [],
  lineHeight: 16,
  marginTop: 5,
  marginRight: 7,
  marginBottom: 2,
  marginLeft: 7,
}

Shorthands will only accept values that are supported in React Native, so background will only accept a colour, backgroundColor will not accept an image, and font will not accept font-variant values that React Native does not support.

React Native's box-shadow and filter properties are passed through as boxShadow and filter, so support depends on your React Native version.

Shorthand Notes

border{Top,Right,Bottom,Left} shorthands are not supported, because borderStyle cannot be applied to individual border sides.

Supported Properties

Most React Native style properties work without a custom mapping table. Write the React Native property name in kebab-case and this library will convert it back to the camel-cased React Native key for you.

CSS input	React Native output
align-content	alignContent
background-color	backgroundColor
border-top-left-radius	borderTopLeftRadius
font-size	fontSize
justify-content	justifyContent
text-decoration-color	textDecorationColor
text-shadow-radius	textShadowRadius

That rule covers the standard one-to-one mappings. The library also supports the following shorthand and special-case transforms:

CSS input	React Native output
aspect-ratio	aspectRatio
background	backgroundColor
border	borderWidth, borderColor, borderStyle
border-color	borderTopColor, borderRightColor, borderBottomColor, borderLeftColor
border-radius	borderTopLeftRadius, borderTopRightRadius, borderBottomRightRadius, borderBottomLeftRadius
border-width	borderTopWidth, borderRightWidth, borderBottomWidth, borderLeftWidth
flex	flexGrow, flexShrink, flexBasis
flex-flow	flexDirection, flexWrap
font	fontStyle, fontWeight, fontVariant, fontSize, lineHeight, fontFamily
font-family	fontFamily
font-variant	fontVariant
font-weight	fontWeight
margin	marginTop, marginRight, marginBottom, marginLeft
padding	paddingTop, paddingRight, paddingBottom, paddingLeft
place-content	alignContent, justifyContent
shadow-offset	shadowOffset
text-decoration	textDecorationLine, textDecorationColor, textDecorationStyle
text-decoration-line	textDecorationLine
text-shadow	textShadowOffset, textShadowRadius, textShadowColor
text-shadow-offset	textShadowOffset
transform	transform
box-shadow	boxShadow passthrough
filter	filter passthrough

If you are unsure whether a property is available in React Native itself, check the React Native style docs and convert the property name to kebab-case when you write it in CSS.

API

The API is mostly for implementors. However, the main API may be useful for non-implementors. The main API is an array of [property, value] tuples.

import transform from 'css-to-react-native';
// or const transform = require('css-to-react-native').default;

transform([
  ['font', 'bold 14px/16px "Helvetica"'],
  ['margin', '5px 7px 2px'],
  ['border-left-width', '5px'],
]); // => { fontFamily: 'Helvetica', ... }

We don't provide a way to get these style tuples in this library, so you'll need to do that yourself. I expect most people will use postCSS or another CSS parser. You should try avoid getting these with string.split, as that has a lot of edge cases (colons and semi-colons appearing in comments etc.)

For implementors, there is also a few extra APIs available.

These are for specific use-cases, and most people should just be using the API above.

import {
  getPropertyName,
  getStylesForProperty,
  transformRawValue,
} from 'css-to-react-native';

getPropertyName('border-width'); // => 'borderWidth'
getStylesForProperty('borderWidth', '1px 0px 2px 0px'); // => { borderTopWidth: 1, ... }
transformRawValue('opacity', '0.5'); // => 0.5

Should you wish to opt-out of transforming certain shorthands, an array of property names in camelCase can be passed as a second argument to transform.

transform([['border-radius', '50px']], ['borderRadius']);
// { borderRadius: 50 } rather than { borderTopLeft: ... }

This can also be done by passing a third argument, false to getStylesForProperty.

transformRawValue is a lower-level helper that parses a single raw value without applying shorthand expansion.

License

Licensed under the MIT License, Copyright © 2019 Krister Kari, Jacob Parker, and Maximilian Stoiber.

See LICENSE.md for more information.