990 lines
22 KiB
Markdown
990 lines
22 KiB
Markdown
<div align="center">
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<img width="180" height="180" vspace="20"
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src="https://cdn.worldvectorlogo.com/logos/css-3.svg">
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<a href="https://github.com/webpack/webpack">
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<img width="200" height="200"
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src="https://webpack.js.org/assets/icon-square-big.svg">
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</a>
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</div>
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[![npm][npm]][npm-url]
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[![node][node]][node-url]
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[![deps][deps]][deps-url]
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[![tests][tests]][tests-url]
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[![coverage][cover]][cover-url]
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[![chat][chat]][chat-url]
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[![size][size]][size-url]
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# css-loader
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The `css-loader` interprets `@import` and `url()` like `import/require()` and will resolve them.
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## Getting Started
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To begin, you'll need to install `css-loader`:
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```console
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npm install --save-dev css-loader
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```
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Then add the plugin to your `webpack` config. For example:
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**file.js**
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```js
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import css from 'file.css';
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```
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**webpack.config.js**
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```js
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module.exports = {
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module: {
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rules: [
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{
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test: /\.css$/i,
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use: ['style-loader', 'css-loader'],
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},
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],
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},
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};
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```
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Good loaders for requiring your assets are the [file-loader](https://github.com/webpack/file-loader) and the [url-loader](https://github.com/webpack/url-loader) which you should specify in your config (see [below](https://github.com/webpack-contrib/css-loader#assets)).
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And run `webpack` via your preferred method.
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### `toString`
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You can also use the css-loader results directly as a string, such as in Angular's component style.
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**webpack.config.js**
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```js
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module.exports = {
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module: {
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rules: [
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{
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test: /\.css$/i,
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use: ['to-string-loader', 'css-loader'],
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},
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],
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},
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};
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```
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or
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```js
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const css = require('./test.css').toString();
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console.log(css); // {String}
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```
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If there are SourceMaps, they will also be included in the result string.
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If, for one reason or another, you need to extract CSS as a
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plain string resource (i.e. not wrapped in a JS module) you
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might want to check out the [extract-loader](https://github.com/peerigon/extract-loader).
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It's useful when you, for instance, need to post process the CSS as a string.
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**webpack.config.js**
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```js
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module.exports = {
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module: {
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rules: [
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{
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test: /\.css$/i,
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use: [
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'handlebars-loader', // handlebars loader expects raw resource string
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'extract-loader',
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'css-loader',
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],
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},
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],
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},
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};
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```
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## Options
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| Name | Type | Default | Description |
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| :-----------------------------------------: | :-------------------------: | :------: | :--------------------------------------------------------------------- |
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| **[`url`](#url)** | `{Boolean\|Function}` | `true` | Enables/Disables `url`/`image-set` functions handling |
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| **[`import`](#import)** | `{Boolean\|Function}` | `true` | Enables/Disables `@import` at-rules handling |
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| **[`modules`](#modules)** | `{Boolean\|String\|Object}` | `false` | Enables/Disables CSS Modules and their configuration |
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| **[`sourceMap`](#sourcemap)** | `{Boolean}` | `false` | Enables/Disables generation of source maps |
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| **[`importLoaders`](#importloaders)** | `{Number}` | `0` | Enables/Disables or setups number of loaders applied before CSS loader |
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| **[`localsConvention`](#localsconvention)** | `{String}` | `'asIs'` | Style of exported classnames |
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| **[`onlyLocals`](#onlylocals)** | `{Boolean}` | `false` | Export only locals |
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| **[`esModule`](#esmodule)** | `{Boolean}` | `false` | Use ES modules syntax |
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### `url`
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Type: `Boolean|Function`
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Default: `true`
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Enables/Disables `url`/`image-set` functions handling.
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Control `url()` resolving. Absolute URLs and root-relative URLs are not resolving.
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Examples resolutions:
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```
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url(image.png) => require('./image.png')
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url('image.png') => require('./image.png')
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url(./image.png) => require('./image.png')
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url('./image.png') => require('./image.png')
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url('http://dontwritehorriblecode.com/2112.png') => require('http://dontwritehorriblecode.com/2112.png')
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image-set(url('image2x.png') 1x, url('image1x.png') 2x) => require('./image1x.png') and require('./image2x.png')
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```
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To import assets from a `node_modules` path (include `resolve.modules`) and for `alias`, prefix it with a `~`:
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```
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url(~module/image.png) => require('module/image.png')
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url('~module/image.png') => require('module/image.png')
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url(~aliasDirectory/image.png) => require('otherDirectory/image.png')
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```
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#### `Boolean`
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Enable/disable `url()` resolving.
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**webpack.config.js**
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```js
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module.exports = {
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module: {
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rules: [
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{
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test: /\.css$/i,
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loader: 'css-loader',
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options: {
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url: true,
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},
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},
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],
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},
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};
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```
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#### `Function`
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Allow to filter `url()`. All filtered `url()` will not be resolved (left in the code as they were written).
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**webpack.config.js**
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```js
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module.exports = {
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module: {
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rules: [
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{
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test: /\.css$/i,
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loader: 'css-loader',
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options: {
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url: (url, resourcePath) => {
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// resourcePath - path to css file
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// Don't handle `img.png` urls
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if (url.includes('img.png')) {
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return false;
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}
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return true;
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},
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},
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},
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],
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},
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};
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```
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### `import`
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Type: `Boolean|Function`
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Default: `true`
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Enables/Disables `@import` at-rules handling.
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Control `@import` resolving. Absolute urls in `@import` will be moved in runtime code.
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Examples resolutions:
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```
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@import 'style.css' => require('./style.css')
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@import url(style.css) => require('./style.css')
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@import url('style.css') => require('./style.css')
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@import './style.css' => require('./style.css')
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@import url(./style.css) => require('./style.css')
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@import url('./style.css') => require('./style.css')
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@import url('http://dontwritehorriblecode.com/style.css') => @import url('http://dontwritehorriblecode.com/style.css') in runtime
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```
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To import styles from a `node_modules` path (include `resolve.modules`) and for `alias`, prefix it with a `~`:
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```
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@import url(~module/style.css) => require('module/style.css')
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@import url('~module/style.css') => require('module/style.css')
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@import url(~aliasDirectory/style.css) => require('otherDirectory/style.css')
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```
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#### `Boolean`
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Enable/disable `@import` resolving.
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**webpack.config.js**
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```js
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module.exports = {
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module: {
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rules: [
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{
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test: /\.css$/i,
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loader: 'css-loader',
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options: {
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import: true,
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},
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},
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],
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},
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};
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```
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#### `Function`
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Allow to filter `@import`. All filtered `@import` will not be resolved (left in the code as they were written).
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**webpack.config.js**
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```js
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module.exports = {
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module: {
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rules: [
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{
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test: /\.css$/i,
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loader: 'css-loader',
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options: {
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import: (parsedImport, resourcePath) => {
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// parsedImport.url - url of `@import`
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// parsedImport.media - media query of `@import`
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// resourcePath - path to css file
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// Don't handle `style.css` import
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if (parsedImport.url.includes('style.css')) {
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return false;
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}
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return true;
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},
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},
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},
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],
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},
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};
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```
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### `modules`
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Type: `Boolean|String|Object`
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Default: `false`
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Enables/Disables CSS Modules and their configuration.
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The `modules` option enables/disables the **[CSS Modules](https://github.com/css-modules/css-modules)** specification and setup basic behaviour.
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Using `false` value increase performance because we avoid parsing **CSS Modules** features, it will be useful for developers who use vanilla css or use other technologies.
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**webpack.config.js**
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```js
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module.exports = {
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module: {
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rules: [
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{
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test: /\.css$/i,
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loader: 'css-loader',
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options: {
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modules: true,
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},
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},
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],
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},
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};
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```
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#### `Features`
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##### `Scope`
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Using `local` value requires you to specify `:global` classes.
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Using `global` value requires you to specify `:local` classes.
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Using `pure` value requires selectors must contain at least one local class or id.
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You can find more information [here](https://github.com/css-modules/css-modules).
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Styles can be locally scoped to avoid globally scoping styles.
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The syntax `:local(.className)` can be used to declare `className` in the local scope. The local identifiers are exported by the module.
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With `:local` (without brackets) local mode can be switched on for this selector.
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The `:global(.className)` notation can be used to declare an explicit global selector.
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With `:global` (without brackets) global mode can be switched on for this selector.
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The loader replaces local selectors with unique identifiers. The chosen unique identifiers are exported by the module.
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```css
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:local(.className) {
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background: red;
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}
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:local .className {
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color: green;
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}
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:local(.className .subClass) {
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color: green;
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}
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:local .className .subClass :global(.global-class-name) {
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color: blue;
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}
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```
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```css
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._23_aKvs-b8bW2Vg3fwHozO {
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background: red;
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}
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._23_aKvs-b8bW2Vg3fwHozO {
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color: green;
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}
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._23_aKvs-b8bW2Vg3fwHozO ._13LGdX8RMStbBE9w-t0gZ1 {
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color: green;
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}
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._23_aKvs-b8bW2Vg3fwHozO ._13LGdX8RMStbBE9w-t0gZ1 .global-class-name {
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color: blue;
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}
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```
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> ℹ️ Identifiers are exported
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```js
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exports.locals = {
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className: '_23_aKvs-b8bW2Vg3fwHozO',
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subClass: '_13LGdX8RMStbBE9w-t0gZ1',
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};
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```
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CamelCase is recommended for local selectors. They are easier to use within the imported JS module.
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You can use `:local(#someId)`, but this is not recommended. Use classes instead of ids.
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##### `Composing`
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When declaring a local classname you can compose a local class from another local classname.
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```css
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:local(.className) {
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background: red;
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color: yellow;
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}
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:local(.subClass) {
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composes: className;
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background: blue;
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}
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```
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This doesn't result in any change to the CSS itself but exports multiple classnames.
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```js
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exports.locals = {
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className: '_23_aKvs-b8bW2Vg3fwHozO',
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subClass: '_13LGdX8RMStbBE9w-t0gZ1 _23_aKvs-b8bW2Vg3fwHozO',
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};
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```
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```css
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._23_aKvs-b8bW2Vg3fwHozO {
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background: red;
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color: yellow;
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}
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._13LGdX8RMStbBE9w-t0gZ1 {
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background: blue;
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}
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```
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##### `Importing`
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To import a local classname from another module.
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```css
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:local(.continueButton) {
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composes: button from 'library/button.css';
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background: red;
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}
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```
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```css
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:local(.nameEdit) {
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composes: edit highlight from './edit.css';
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background: red;
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}
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```
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To import from multiple modules use multiple `composes:` rules.
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```css
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:local(.className) {
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composes: edit hightlight from './edit.css';
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composes: button from 'module/button.css';
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composes: classFromThisModule;
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background: red;
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}
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```
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##### `Values`
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You can use `@value` to specific values to be reused throughout a document.
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We recommend use prefix `v-` for values, `s-` for selectors and `m-` for media at-rules.
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```css
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@value v-primary: #BF4040;
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@value s-black: black-selector;
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@value m-large: (min-width: 960px);
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.header {
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color: v-primary;
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padding: 0 10px;
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}
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.s-black {
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color: black;
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}
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@media m-large {
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.header {
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padding: 0 20px;
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}
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}
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```
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#### `Boolean`
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Enable **CSS Modules** features.
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**webpack.config.js**
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```js
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module.exports = {
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module: {
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rules: [
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{
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test: /\.css$/i,
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loader: 'css-loader',
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options: {
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modules: true,
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},
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},
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],
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},
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};
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```
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#### `String`
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Enable **CSS Modules** features and setup `mode`.
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**webpack.config.js**
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```js
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module.exports = {
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module: {
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rules: [
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{
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test: /\.css$/i,
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loader: 'css-loader',
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options: {
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// Using `local` value has same effect like using `modules: true`
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modules: 'global',
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},
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},
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],
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},
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};
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```
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#### `Object`
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Enable **CSS Modules** features and setup options for them.
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**webpack.config.js**
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```js
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module.exports = {
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module: {
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rules: [
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{
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test: /\.css$/i,
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loader: 'css-loader',
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options: {
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modules: {
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mode: 'local',
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localIdentName: '[path][name]__[local]--[hash:base64:5]',
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context: path.resolve(__dirname, 'src'),
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hashPrefix: 'my-custom-hash',
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},
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},
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},
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],
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},
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};
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```
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##### `mode`
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Type: `String`
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Default: `'local'`
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Setup `mode` option. You can omit the value when you want `local` mode.
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**webpack.config.js**
|
||
|
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```js
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module.exports = {
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module: {
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rules: [
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{
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test: /\.css$/i,
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loader: 'css-loader',
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options: {
|
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modules: {
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mode: 'global',
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},
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},
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},
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],
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},
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};
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```
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##### `localIdentName`
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Type: `String`
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Default: `'[hash:base64]'`
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You can configure the generated ident with the `localIdentName` query parameter.
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See [loader-utils's documentation](https://github.com/webpack/loader-utils#interpolatename) for more information on options.
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Recommendations:
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- use `'[path][name]__[local]'` for development
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- use `'[hash:base64]'` for production
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The `[local]` placeholder contains original class.
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**Note:** all reserved (`<>:"/\|?*`) and control filesystem characters (excluding characters in the `[local]` placeholder) will be converted to `-`.
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|
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**webpack.config.js**
|
||
|
||
```js
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module.exports = {
|
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module: {
|
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rules: [
|
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{
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test: /\.css$/i,
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loader: 'css-loader',
|
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options: {
|
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modules: {
|
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localIdentName: '[path][name]__[local]--[hash:base64:5]',
|
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},
|
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},
|
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},
|
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],
|
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},
|
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};
|
||
```
|
||
|
||
##### `context`
|
||
|
||
Type: `String`
|
||
Default: `undefined`
|
||
|
||
Allow to redefine basic loader context for local ident name.
|
||
By default we use `rootContext` of loader.
|
||
|
||
**webpack.config.js**
|
||
|
||
```js
|
||
module.exports = {
|
||
module: {
|
||
rules: [
|
||
{
|
||
test: /\.css$/i,
|
||
loader: 'css-loader',
|
||
options: {
|
||
modules: {
|
||
context: path.resolve(__dirname, 'context'),
|
||
},
|
||
},
|
||
},
|
||
],
|
||
},
|
||
};
|
||
```
|
||
|
||
##### `hashPrefix`
|
||
|
||
Type: `String`
|
||
Default: `undefined`
|
||
|
||
Allow to add custom hash to generate more unique classes.
|
||
|
||
**webpack.config.js**
|
||
|
||
```js
|
||
module.exports = {
|
||
module: {
|
||
rules: [
|
||
{
|
||
test: /\.css$/i,
|
||
loader: 'css-loader',
|
||
options: {
|
||
modules: {
|
||
hashPrefix: 'hash',
|
||
},
|
||
},
|
||
},
|
||
],
|
||
},
|
||
};
|
||
```
|
||
|
||
##### `getLocalIdent`
|
||
|
||
Type: `Function`
|
||
Default: `undefined`
|
||
|
||
You can also specify the absolute path to your custom `getLocalIdent` function to generate classname based on a different schema.
|
||
By default we use built-in function to generate a classname.
|
||
|
||
**webpack.config.js**
|
||
|
||
```js
|
||
module.exports = {
|
||
module: {
|
||
rules: [
|
||
{
|
||
test: /\.css$/i,
|
||
loader: 'css-loader',
|
||
options: {
|
||
modules: {
|
||
getLocalIdent: (context, localIdentName, localName, options) => {
|
||
return 'whatever_random_class_name';
|
||
},
|
||
},
|
||
},
|
||
},
|
||
],
|
||
},
|
||
};
|
||
```
|
||
|
||
##### `localIdentRegExp`
|
||
|
||
Type: `String|RegExp`
|
||
Default: `undefined`
|
||
|
||
**webpack.config.js**
|
||
|
||
```js
|
||
module.exports = {
|
||
module: {
|
||
rules: [
|
||
{
|
||
test: /\.css$/i,
|
||
loader: 'css-loader',
|
||
options: {
|
||
modules: {
|
||
localIdentRegExp: /page-(.*)\.css/i,
|
||
},
|
||
},
|
||
},
|
||
],
|
||
},
|
||
};
|
||
```
|
||
|
||
### `sourceMap`
|
||
|
||
Type: `Boolean`
|
||
Default: `false`
|
||
|
||
Enables/Disables generation of source maps.
|
||
|
||
To include source maps set the `sourceMap` option.
|
||
|
||
They are not enabled by default because they expose a runtime overhead and increase in bundle size (JS source maps do not).
|
||
|
||
**webpack.config.js**
|
||
|
||
```js
|
||
module.exports = {
|
||
module: {
|
||
rules: [
|
||
{
|
||
test: /\.css$/i,
|
||
loader: 'css-loader',
|
||
options: {
|
||
sourceMap: true,
|
||
},
|
||
},
|
||
],
|
||
},
|
||
};
|
||
```
|
||
|
||
### `importLoaders`
|
||
|
||
Type: `Number`
|
||
Default: `0`
|
||
|
||
Enables/Disables or setups number of loaders applied before CSS loader.
|
||
|
||
The option `importLoaders` allows you to configure how many loaders before `css-loader` should be applied to `@import`ed resources.
|
||
|
||
**webpack.config.js**
|
||
|
||
```js
|
||
module.exports = {
|
||
module: {
|
||
rules: [
|
||
{
|
||
test: /\.css$/i,
|
||
use: [
|
||
'style-loader',
|
||
{
|
||
loader: 'css-loader',
|
||
options: {
|
||
importLoaders: 2,
|
||
// 0 => no loaders (default);
|
||
// 1 => postcss-loader;
|
||
// 2 => postcss-loader, sass-loader
|
||
},
|
||
},
|
||
'postcss-loader',
|
||
'sass-loader',
|
||
],
|
||
},
|
||
],
|
||
},
|
||
};
|
||
```
|
||
|
||
This may change in the future when the module system (i. e. webpack) supports loader matching by origin.
|
||
|
||
### `localsConvention`
|
||
|
||
Type: `String`
|
||
Default: `'asIs'`
|
||
|
||
Style of exported classnames.
|
||
|
||
By default, the exported JSON keys mirror the class names (i.e `asIs` value).
|
||
|
||
| Name | Type | Description |
|
||
| :-------------------: | :--------: | :----------------------------------------------------------------------------------------------- |
|
||
| **`'asIs'`** | `{String}` | Class names will be exported as is. |
|
||
| **`'camelCase'`** | `{String}` | Class names will be camelized, the original class name will not to be removed from the locals |
|
||
| **`'camelCaseOnly'`** | `{String}` | Class names will be camelized, the original class name will be removed from the locals |
|
||
| **`'dashes'`** | `{String}` | Only dashes in class names will be camelized |
|
||
| **`'dashesOnly'`** | `{String}` | Dashes in class names will be camelized, the original class name will be removed from the locals |
|
||
|
||
**file.css**
|
||
|
||
```css
|
||
.class-name {
|
||
}
|
||
```
|
||
|
||
**file.js**
|
||
|
||
```js
|
||
import { className } from 'file.css';
|
||
```
|
||
|
||
**webpack.config.js**
|
||
|
||
```js
|
||
module.exports = {
|
||
module: {
|
||
rules: [
|
||
{
|
||
test: /\.css$/i,
|
||
loader: 'css-loader',
|
||
options: {
|
||
localsConvention: 'camelCase',
|
||
},
|
||
},
|
||
],
|
||
},
|
||
};
|
||
```
|
||
|
||
### `onlyLocals`
|
||
|
||
Type: `Boolean`
|
||
Default: `false`
|
||
|
||
Export only locals.
|
||
|
||
**Useful** when you use **css modules** for pre-rendering (for example SSR).
|
||
For pre-rendering with `mini-css-extract-plugin` you should use this option instead of `style-loader!css-loader` **in the pre-rendering bundle**.
|
||
It doesn't embed CSS but only exports the identifier mappings.
|
||
|
||
**webpack.config.js**
|
||
|
||
```js
|
||
module.exports = {
|
||
module: {
|
||
rules: [
|
||
{
|
||
test: /\.css$/i,
|
||
loader: 'css-loader',
|
||
options: {
|
||
onlyLocals: true,
|
||
},
|
||
},
|
||
],
|
||
},
|
||
};
|
||
```
|
||
|
||
### `esModule`
|
||
|
||
Type: `Boolean`
|
||
Default: `false`
|
||
|
||
By default, `css-loader` generates JS modules that use the CommonJS modules syntax.
|
||
There are some cases in which using ES modules is beneficial, like in the case of [module concatenation](https://webpack.js.org/plugins/module-concatenation-plugin/) and [tree shaking](https://webpack.js.org/guides/tree-shaking/).
|
||
|
||
You can enable a ES module syntax using:
|
||
|
||
**webpack.config.js**
|
||
|
||
```js
|
||
module.exports = {
|
||
module: {
|
||
rules: [
|
||
{
|
||
test: /\.css$/i,
|
||
loader: 'css-loader',
|
||
options: {
|
||
esModule: true,
|
||
},
|
||
},
|
||
],
|
||
},
|
||
};
|
||
```
|
||
|
||
## Examples
|
||
|
||
### Assets
|
||
|
||
The following `webpack.config.js` can load CSS files, embed small PNG/JPG/GIF/SVG images as well as fonts as [Data URLs](https://tools.ietf.org/html/rfc2397) and copy larger files to the output directory.
|
||
|
||
**webpack.config.js**
|
||
|
||
```js
|
||
module.exports = {
|
||
module: {
|
||
rules: [
|
||
{
|
||
test: /\.css$/i,
|
||
use: ['style-loader', 'css-loader'],
|
||
},
|
||
{
|
||
test: /\.(png|jpe?g|gif|svg|eot|ttf|woff|woff2)$/i,
|
||
loader: 'url-loader',
|
||
options: {
|
||
limit: 8192,
|
||
},
|
||
},
|
||
],
|
||
},
|
||
};
|
||
```
|
||
|
||
### Extract
|
||
|
||
For production builds it's recommended to extract the CSS from your bundle being able to use parallel loading of CSS/JS resources later on.
|
||
|
||
- This can be achieved by using the [mini-css-extract-plugin](https://github.com/webpack-contrib/mini-css-extract-plugin) to extract the CSS when running in production mode.
|
||
|
||
- As an alternative, if seeking better development performance and css outputs that mimic production. [extract-css-chunks-webpack-plugin](https://github.com/faceyspacey/extract-css-chunks-webpack-plugin) offers a hot module reload friendly, extended version of mini-css-extract-plugin. HMR real CSS files in dev, works like mini-css in non-dev
|
||
|
||
### CSS modules and pure CSS
|
||
|
||
When you have pure CSS (without CSS modules) and CSS modules in project you can use this setup:
|
||
|
||
**webpack.config.js**
|
||
|
||
```js
|
||
module.exports = {
|
||
module: {
|
||
rules: [
|
||
{
|
||
// For pure CSS (without CSS modules)
|
||
test: /\.css$/i,
|
||
exclude: /\.module\.css$/i,
|
||
use: ['style-loader', 'css-loader'],
|
||
},
|
||
{
|
||
// For CSS modules
|
||
test: /\.module\.css$/i,
|
||
use: [
|
||
'style-loader',
|
||
{
|
||
loader: 'css-loader',
|
||
options: {
|
||
modules: true,
|
||
},
|
||
},
|
||
],
|
||
},
|
||
{
|
||
test: /\.(png|jpe?g|gif|svg|eot|ttf|woff|woff2)$/i,
|
||
loader: 'url-loader',
|
||
options: {
|
||
limit: 8192,
|
||
},
|
||
},
|
||
],
|
||
},
|
||
};
|
||
```
|
||
|
||
## Contributing
|
||
|
||
Please take a moment to read our contributing guidelines if you haven't yet done so.
|
||
|
||
[CONTRIBUTING](./.github/CONTRIBUTING.md)
|
||
|
||
## License
|
||
|
||
[MIT](./LICENSE)
|
||
|
||
[npm]: https://img.shields.io/npm/v/css-loader.svg
|
||
[npm-url]: https://npmjs.com/package/css-loader
|
||
[node]: https://img.shields.io/node/v/css-loader.svg
|
||
[node-url]: https://nodejs.org
|
||
[deps]: https://david-dm.org/webpack-contrib/css-loader.svg
|
||
[deps-url]: https://david-dm.org/webpack-contrib/css-loader
|
||
[tests]: https://dev.azure.com/webpack-contrib/css-loader/_apis/build/status/webpack-contrib.css-loader?branchName=master
|
||
[tests-url]: https://dev.azure.com/webpack-contrib/css-loader/_build/latest?definitionId=2&branchName=master
|
||
[cover]: https://codecov.io/gh/webpack-contrib/css-loader/branch/master/graph/badge.svg
|
||
[cover-url]: https://codecov.io/gh/webpack-contrib/css-loader
|
||
[chat]: https://badges.gitter.im/webpack/webpack.svg
|
||
[chat-url]: https://gitter.im/webpack/webpack
|
||
[size]: https://packagephobia.now.sh/badge?p=css-loader
|
||
[size-url]: https://packagephobia.now.sh/result?p=css-loader
|