css-to-react-native-transform
A lightweight wrapper on top of
css-to-react-native
to allow valid CSS to be turned into React Native Stylesheet objects.
To keep things simple it only transforms class selectors (e.g. .myClass {}
) and grouped class selectors (e.g. .myClass, .myOtherClass {}
). Parsing of more complex selectors can be added as a new feature behind a feature flag (e.g. transform(css, { parseAllSelectors: true })
) in the future if needed.
Example:
.myClass {
font-size: 18px;
line-height: 24px;
color: red;
}
.other {
padding: 1rem;
}
is transformed to:
{
myClass: {
fontSize: 18,
lineHeight: 24,
color: "red"
},
other: {
paddingBottom: 16,
paddingLeft: 16,
paddingRight: 16,
paddingTop: 16
}
}
API
Transform CSS
import transform from "css-to-react-native-transform";
transform(`
.foo {
color: #f00;
}
`);
↓ ↓ ↓ ↓ ↓ ↓
{
foo: {
color: "#f00";
}
}
ignoreRule
option
transform(
`
.foo {
color: red;
}
.bar {
font-size: 12px;
}
`,
{
ignoreRule: (selector) => {
if (selector === ".foo") {
return true;
}
},
},
);
↓ ↓ ↓ ↓ ↓ ↓
{
bar: {
fontSize: 12;
}
}
CSS Modules :export block
Parsing the CSS Modules (ICSS) :export is supported. The :export
is often used to share variables from CSS or from a preprocessor like Sass/Less/Stylus to Javascript:
transform(`
.foo {
color: #f00;
}
:export {
myProp: #fff;
}
`);
↓ ↓ ↓ ↓ ↓ ↓
{
foo: {
color: "#f00";
},
myProp: "#fff";
}
CSS Media Queries (experimental)
The API and parsed syntax for CSS Media Queries might change in the future
transform(
`
.container {
background-color: #f00;
}
@media (orientation: landscape) {
.container {
background-color: #00f;
}
}
`,
{ parseMediaQueries: true },
);
↓ ↓ ↓ ↓ ↓ ↓
{
__mediaQueries: {
"@media (orientation: landscape)": [{
expressions: [
{
feature: "orientation",
modifier: undefined,
value: "landscape",
},
],
inverse: false,
type: "all",
}],
},
container: {
backgroundColor: "#f00",
},
"@media (orientation: landscape)": {
container: {
backgroundColor: "#00f",
},
},
}
You can also speficy a platform as the media query type ("android", "dom", "ios", "macos", "web", "windows"):
transform(
`
.container {
background-color: #f00;
}
@media android and (orientation: landscape) {
.container {
background-color: #00f;
}
}
`,
{ parseMediaQueries: true },
);
CSS Viewport Units (experimental)
When CSS Viewport Units are used, a special __viewportUnits
feature flag is added to the result. This is done so that the implementation that transforms viewport units to pixels knows that the style object has viewport units inside it, and can avoid doing extra work if the style object does not contain any viewport units.
transform(`.foo { font-size: 1vh; }`);
↓ ↓ ↓ ↓ ↓ ↓
{
__viewportUnits: true,
foo: {
fontSize: "1vh";
}
}
Limitations
- For
rem
unit the root element font-size
is currently set to 16 pixels. A
setting needs to be implemented to allow the user to define the root element
font-size
. - There is also support for the
box-shadow
shorthand, and this converts into
shadow-
properties. Note that these only work on iOS.
Dependencies
This library has the following packages as dependencies:
- css - CSS parser / stringifier
- css-mediaquery - Parses and determines if a given CSS Media Query matches a set of values.
- css-to-react-native - Convert CSS text to a React Native stylesheet object