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https://github.com/kristerkari/react-native-less-transformer
Use Less to style your React Native apps.
https://github.com/kristerkari/react-native-less-transformer
less loader react-native transform
Last synced: 9 days ago
JSON representation
Use Less to style your React Native apps.
- Host: GitHub
- URL: https://github.com/kristerkari/react-native-less-transformer
- Owner: kristerkari
- License: mit
- Created: 2018-04-07T23:23:22.000Z (almost 7 years ago)
- Default Branch: master
- Last Pushed: 2024-09-12T01:20:41.000Z (5 months ago)
- Last Synced: 2025-01-16T12:32:03.749Z (16 days ago)
- Topics: less, loader, react-native, transform
- Language: JavaScript
- Homepage:
- Size: 654 KB
- Stars: 31
- Watchers: 3
- Forks: 10
- Open Issues: 12
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
Awesome Lists containing this project
README
# react-native-less-transformer [](https://www.npmjs.org/package/react-native-less-transformer) [](http://npmcharts.com/compare/react-native-less-transformer?periodLength=30) [](https://egghead.io/courses/how-to-contribute-to-an-open-source-project-on-github)
Use [Less](http://lesscss.org/) to style your React Native apps.
Behind the scenes the `.less` files are transformed to [react native style objects](https://facebook.github.io/react-native/docs/style.html) (look at the examples).
> This transformer can be used together with [React Native CSS modules](https://github.com/kristerkari/react-native-css-modules).
## How does it work?
Your `App.less` file might look like this:
```less
@nice-blue: #5b83ad;
@light-blue: @nice-blue + #111;
.myClass {
color: @light-blue;
}
.myOtherClass {
color: red;
}
.my-dashed-class {
color: green;
}
```
When you import your stylesheet:
```js
import styles from "./App.less";
```
Your imported styles will look like this:
```js
var styles = {
myClass: {
color: "#6c94be"
},
myOtherClass: {
color: "red"
},
"my-dashed-class": {
color: "green"
}
};
```
You can then use that style object with an element:
**Plain React Native:**
```jsx
```
**[React Native CSS modules](https://github.com/kristerkari/react-native-css-modules) using [className](https://github.com/kristerkari/babel-plugin-react-native-classname-to-style) property:**
```jsx
```
**[React Native CSS modules](https://github.com/kristerkari/react-native-css-modules) using [styleName](https://github.com/kristerkari/babel-plugin-react-native-stylename-to-style) property:**
```jsx
```
## Installation and configuration
_Minimum React Native version for this transformer is 0.52. If you are using an older version, please update to a newer React Native version before trying to use this transformer._
### Step 1: Install
```sh
npm install --save-dev react-native-less-transformer less
```
or
```sh
yarn add --dev react-native-less-transformer less
```
### Step 2: Configure the react native packager
#### For Expo SDK v41.0.0 or newer
Merge the contents from your project's `metro.config.js` file with this config (create the file if it does not exist already).
`metro.config.js`:
```js
const { getDefaultConfig } = require("expo/metro-config");
module.exports = (() => {
const config = getDefaultConfig(__dirname);
const { transformer, resolver } = config;
config.transformer = {
...transformer,
babelTransformerPath: require.resolve("react-native-less-transformer")
};
config.resolver = {
...resolver,
sourceExts: [...sourceExts, "less"]
};
return config;
})();
```
---
#### For React Native v0.72.1 or newer
Merge the contents from your project's `metro.config.js` file with this config (create the file if it does not exist already).
`metro.config.js`:
```js
const { getDefaultConfig, mergeConfig } = require("@react-native/metro-config");
const defaultConfig = getDefaultConfig(__dirname);
const { assetExts, sourceExts } = defaultConfig.resolver;
/**
* Metro configuration
* https://reactnative.dev/docs/metro
*
* @type {import('metro-config').MetroConfig}
*/
const config = {
transformer: {
babelTransformerPath: require.resolve("react-native-less-transformer")
},
resolver: {
sourceExts: [...sourceExts, "less"]
}
};
module.exports = mergeConfig(defaultConfig, config);
```
## LESS options
If you need to pass options (e.g. plugins) to `less`, you can do so by creating a `transformer.js` file and doing the following:
```js
const upstreamTransformer = require("@react-native/metro-babel-transformer");
const lessTransformer = require("react-native-less-transformer");
module.exports.transform = function ({ src, filename, options, ...rest }) {
if (filename.endsWith(".less")) {
var opts = Object.assign(options, {
lessOptions: {
plugins: [require("less-plugin-glob")]
}
});
return lessTransformer.transform({ src, filename, options: opts, ...rest });
} else {
return upstreamTransformer.transform({ src, filename, options, ...rest });
}
};
```
After that in `metro.config.js` point the `babelTransformerPath` to that file:
```diff
-require.resolve("react-native-less-transformer")
+require.resolve("./transformer.js")
```
## CSS Custom Properties (CSS variables)
_You need version 1.2.1 or newer_
```css
:root {
--text-color: blue;
}
.blue {
color: var(--text-color);
}
```
CSS variables are not supported by default, but you can add support for them by using [PostCSS](https://postcss.org/) and [postcss-css-variables](https://github.com/MadLittleMods/postcss-css-variables#readme) plugin.
Start by installing dependencies:
```sh
npm install postcss postcss-css-variables react-native-postcss-transformer --save-dev
```
or
```sh
yarn add postcss postcss-css-variables react-native-postcss-transformer --dev
```
Add `postcss-css-variables` to your PostCSS configuration with [one of the supported config formats](https://github.com/michael-ciniawsky/postcss-load-config), e.g. `package.json`, `.postcssrc`, `postcss.config.js`, etc.
After that create a `transformer.js` file and do the following:
```js
const upstreamTransformer = require("@react-native/metro-babel-transformer");
const lessTransformer = require("react-native-less-transformer");
const postCSSTransformer = require("react-native-postcss-transformer");
module.exports.transform = function ({ src, filename, ...rest }) {
if (filename.endsWith(".less")) {
return lessTransformer
.renderToCSS({ src, filename, options })
.then((css) =>
postCSSTransformer.transform({ src: css, filename, ...rest })
);
} else {
return upstreamTransformer.transform({ src, filename, ...rest });
}
};
```
After that in `metro.config.js` point the `babelTransformerPath` to that file:
```diff
-require.resolve("react-native-less-transformer")
+require.resolve("./transformer.js")
```
## Dependencies
This library has the following Node.js modules as dependencies:
- [app-root-path](https://github.com/inxilpro/node-app-root-path)
- [css-to-react-native-transform](https://github.com/kristerkari/css-to-react-native-transform)