607 lines
16 KiB
Markdown
607 lines
16 KiB
Markdown
<div align="center">
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<img height="100"
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src="https://worldvectorlogo.com/logos/sass-1.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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# sass-loader
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Loads a Sass/SCSS file and compiles it to CSS.
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## Getting Started
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To begin, you'll need to install `sass-loader`:
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```console
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npm install sass-loader node-sass webpack --save-dev
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```
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`sass-loader` requires you to install either [Node Sass](https://github.com/sass/node-sass) or [Dart Sass](https://github.com/sass/dart-sass) on your own (more documentation can be found below).
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This allows you to control the versions of all your dependencies, and to choose which Sass implementation to use.
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Chain the `sass-loader` with the [css-loader](https://github.com/webpack-contrib/css-loader) and the [style-loader](https://github.com/webpack-contrib/style-loader) to immediately apply all styles to the DOM or the [mini-css-extract-plugin](https://github.com/webpack-contrib/mini-css-extract-plugin) to extract it into a separate file.
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Then add the loader to your Webpack configuration. For example:
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**app.js**
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```js
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import './style.scss';
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```
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**style.scss**
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```scss
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$body-color: red;
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body {
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color: $body-color;
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}
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```
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**webpack.config.js**
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```js
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module.exports = {
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module: {
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rules: [
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{
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test: /\.s[ac]ss$/i,
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use: [
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// Creates `style` nodes from JS strings
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'style-loader',
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// Translates CSS into CommonJS
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'css-loader',
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// Compiles Sass to CSS
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'sass-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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Finally run `webpack` via your preferred method.
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### Resolving `import` at-rules
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Webpack provides an [advanced mechanism to resolve files](https://webpack.js.org/concepts/module-resolution/).
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The `sass-loader` uses Sass's custom importer feature to pass all queries to the Webpack resolving engine. Thus you can import your Sass modules from `node_modules`. Just prepend them with a `~` to tell Webpack that this is not a relative import:
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```scss
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@import '~bootstrap';
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```
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It's important to only prepend it with `~`, because `~/` resolves to the home directory.
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Webpack needs to distinguish between `bootstrap` and `~bootstrap` because CSS and Sass files have no special syntax for importing relative files.
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Writing `@import "style.scss"` is the same as `@import "./style.scss";`
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### Problems with `url(...)`
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Since Sass implementations don't provide [url rewriting](https://github.com/sass/libsass/issues/532), all linked assets must be relative to the output.
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- If you pass the generated CSS on to the `css-loader`, all urls must be relative to the entry-file (e.g. `main.scss`).
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- If you're just generating CSS without passing it to the `css-loader`, it must be relative to your web root.
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You will be disrupted by this first issue. It is natural to expect relative references to be resolved against the `.sass`/`.scss` file in which they are specified (like in regular `.css` files).
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Thankfully there are a two solutions to this problem:
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- Add the missing url rewriting using the [resolve-url-loader](https://github.com/bholloway/resolve-url-loader). Place it before `sass-loader` in the loader chain.
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- Library authors usually provide a variable to modify the asset path. [bootstrap-sass](https://github.com/twbs/bootstrap-sass) for example has an `$icon-font-path`.
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## Options
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### `implementation`
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The special `implementation` option determines which implementation of Sass to use.
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By default the loader resolve the implementation based on your dependencies.
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Just add required implementation to `package.json` (`node-sass` or `sass` package) and install dependencies.
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Example where the `sass-loader` loader uses the `sass` (`dart-sass`) implementation:
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**package.json**
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```json
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{
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"devDependencies": {
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"sass-loader": "^7.2.0",
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"sass": "^1.22.10"
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}
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}
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```
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Example where the `sass-loader` loader uses the `node-sass` implementation:
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**package.json**
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```json
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{
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"devDependencies": {
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"sass-loader": "^7.2.0",
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"node-sass": "^4.0.0"
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}
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}
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```
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Beware the situation when `node-sass` and `sass` were installed! By default the `sass-loader` prefers `node-sass`. In order to avoid this situation you can use the `implementation` option.
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The `implementation` options either accepts `node-sass` or `sass` (`Dart Sass`) as a module.
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For example, to use Dart Sass, you'd pass:
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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: /\.s[ac]ss$/i,
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use: [
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'style-loader',
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'css-loader',
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{
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loader: 'sass-loader',
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options: {
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// Prefer `dart-sass`
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implementation: require('sass'),
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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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```
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Note that when using `sass` (`Dart Sass`), **synchronous compilation is twice as fast as asynchronous compilation** by default, due to the overhead of asynchronous callbacks.
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To avoid this overhead, you can use the [fibers](https://www.npmjs.com/package/fibers) package to call asynchronous importers from the synchronous code path.
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We automatically inject the [`fibers`](https://github.com/laverdet/node-fibers) package (setup `sassOptions.fiber`) if is possible (i.e. you need install the [`fibers`](https://github.com/laverdet/node-fibers) package).
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**package.json**
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```json
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{
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"devDependencies": {
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"sass-loader": "^7.2.0",
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"sass": "^1.22.10",
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"fibers": "^4.0.1"
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}
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}
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```
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You can disable automatically injecting the [`fibers`](https://github.com/laverdet/node-fibers) package by passing a `false` value for the `sassOptions.fiber` option.
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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: /\.s[ac]ss$/i,
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use: [
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'style-loader',
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'css-loader',
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{
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loader: 'sass-loader',
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options: {
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implementation: require('sass'),
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sassOptions: {
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fiber: false,
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},
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},
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},
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],
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},
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],
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},
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};
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```
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You can also pass the `fiber` value using this code:
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**webpack.config.js**
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```js
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module.exports = {
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module: {
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rules: [
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{
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test: /\.s[ac]ss$/i,
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use: [
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'style-loader',
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'css-loader',
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{
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loader: 'sass-loader',
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options: {
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implementation: require('sass'),
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sassOptions: {
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fiber: require('fibers'),
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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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};
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```
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### `sassOptions`
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Type: `Object|Function`
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Options for [Node Sass](https://github.com/sass/node-sass) or [Dart Sass](http://sass-lang.com/dart-sass) implementation.
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> ℹ️ The `indentedSyntax` option has `true` value for the `sass` extension.
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> ℹ️ Options such as `file` and `outFile` are unavailable.
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> ℹ We recommend not to use the `sourceMapContents`, `sourceMapEmbed`, `sourceMapRoot` options because `sass-loader` automatically sets these options.
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There is a slight difference between the `node-sass` and `sass` (`Dart Sass`) options.
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Please consult documentation before using them:
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- [Node Sass documentation](https://github.com/sass/node-sass/#options) for all available `node-sass` options.
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- [Dart Sass documentation](https://github.com/sass/dart-sass#javascript-api) for all available `sass` options.
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#### `Object`
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Use and object for the Sass implementation setup.
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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: /\.s[ac]ss$/i,
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use: [
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'style-loader',
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'css-loader',
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{
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loader: 'sass-loader',
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options: {
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sassOptions: {
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indentWidth: 4,
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includePaths: ['absolute/path/a', 'absolute/path/b'],
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},
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},
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},
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],
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},
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],
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},
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};
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```
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#### `Function`
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Allows to setup the Sass implementation by setting different options based on the loader context.
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```js
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module.exports = {
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module: {
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rules: [
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{
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test: /\.s[ac]ss$/i,
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use: [
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'style-loader',
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'css-loader',
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{
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loader: 'sass-loader',
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options: {
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sassOptions: (loaderContext) => {
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// More information about available properties https://webpack.js.org/api/loaders/
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const { resourcePath, rootContext } = loaderContext;
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const relativePath = path.relative(rootContext, resourcePath);
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if (relativePath === 'styles/foo.scss') {
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return {
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includePaths: ['absolute/path/c', 'absolute/path/d'],
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};
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}
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return {
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includePaths: ['absolute/path/a', 'absolute/path/b'],
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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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},
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};
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```
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### `prependData`
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Type: `String|Function`
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Default: `undefined`
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Prepends `Sass`/`SCSS` code before the actual entry file.
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In this case, the `sass-loader` will not override the `data` option but just append the entry's content.
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This is especially useful when some of your Sass variables depend on the environment:
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> ℹ Since you're injecting code, this will break the source mappings in your entry file. Often there's a simpler solution than this, like multiple Sass entry files.
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#### `String`
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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: /\.s[ac]ss$/i,
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use: [
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'style-loader',
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'css-loader',
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{
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loader: 'sass-loader',
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options: {
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prependData: '$env: ' + process.env.NODE_ENV + ';',
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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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```
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#### `Function`
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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: /\.s[ac]ss$/i,
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use: [
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'style-loader',
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'css-loader',
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{
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loader: 'sass-loader',
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options: {
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prependData: (loaderContext) => {
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// More information about available properties https://webpack.js.org/api/loaders/
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const { resourcePath, rootContext } = loaderContext;
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const relativePath = path.relative(rootContext, resourcePath);
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if (relativePath === 'styles/foo.scss') {
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return '$value: 100px;';
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}
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return '$value: 200px;';
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},
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},
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},
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],
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},
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],
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},
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};
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```
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### `sourceMap`
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Type: `Boolean`
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Default: depends on the `compiler.devtool` value
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Enables/Disables generation of source maps.
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By default generation of source maps depends on the [`devtool`](https://webpack.js.org/configuration/devtool/) option. All values enable source map generation except `eval` and `false` value.
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**webpack.config.js**
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```js
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module.exports = {
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module: {
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rules: [
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{
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test: /\.s[ac]ss$/i,
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use: [
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'style-loader',
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{
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loader: 'css-loader',
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options: {
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sourceMap: true,
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},
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},
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{
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loader: 'sass-loader',
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options: {
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sourceMap: 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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```
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> ℹ In some rare cases `node-sass` can output invalid source maps (it is a `node-sass` bug).
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> In order to avoid this, you can try to update `node-sass` to latest version or you can try to set within `sassOptions` the `outputStyle` option to `compressed`.
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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: /\.s[ac]ss$/i,
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use: [
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'style-loader',
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'css-loader',
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{
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loader: 'sass-loader',
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sourceMap: true,
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sassOptions: {
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outputStyle: 'compressed',
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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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```
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### `webpackImporter`
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Type: `Boolean`
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Default: `true`
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Enables/Disables the default Webpack importer.
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This can improve performance in some cases. Use it with caution because aliases and `@import` at-rules starting with `~` will not work. You can pass own `importer` to solve this (see [`importer docs`](https://github.com/sass/node-sass#importer--v200---experimental)).
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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: /\.s[ac]ss$/i,
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use: [
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'style-loader',
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'css-loader',
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{
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loader: 'sass-loader',
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options: {
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webpackImporter: false,
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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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```
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## Examples
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### Extracts CSS into separate files
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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.
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There are two possibilities to extract a style sheet from the bundle:
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- [mini-css-extract-plugin](https://github.com/webpack-contrib/mini-css-extract-plugin) (use this, when using webpack 4 configuration. Works in all use-cases)
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- [extract-loader](https://github.com/peerigon/extract-loader) (simpler, but specialized on the css-loader's output)
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**webpack.config.js**
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```js
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const MiniCssExtractPlugin = require('mini-css-extract-plugin');
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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: /\.s[ac]ss$/i,
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use: [
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// fallback to style-loader in development
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process.env.NODE_ENV !== 'production'
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? 'style-loader'
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: MiniCssExtractPlugin.loader,
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'css-loader',
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'sass-loader',
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],
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},
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],
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},
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plugins: [
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new MiniCssExtractPlugin({
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// Options similar to the same options in webpackOptions.output
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// both options are optional
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filename: '[name].css',
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chunkFilename: '[id].css',
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}),
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],
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};
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```
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### Source maps
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Enables/Disables generation of source maps.
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To enable CSS source maps, you'll need to pass the `sourceMap` option to the `sass-loader` _and_ the css-loader.
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**webpack.config.js**
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```javascript
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module.exports = {
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devtool: 'source-map', // any "source-map"-like devtool is possible
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module: {
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rules: [
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{
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test: /\.scss$/,
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use: [
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'style-loader',
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{
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loader: 'css-loader',
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options: {
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sourceMap: true,
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},
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},
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{
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loader: 'sass-loader',
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options: {
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sourceMap: 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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```
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If you want to edit the original Sass files inside Chrome, [there's a good blog post](https://medium.com/@toolmantim/getting-started-with-css-sourcemaps-and-in-browser-sass-editing-b4daab987fb0). Checkout [test/sourceMap](https://github.com/webpack-contrib/sass-loader/tree/master/test) for a running example.
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## Contributing
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||
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Please take a moment to read our contributing guidelines if you haven't yet done so.
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[CONTRIBUTING](./.github/CONTRIBUTING.md)
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||
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||
## License
|
||
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||
[MIT](./LICENSE)
|
||
|
||
[npm]: https://img.shields.io/npm/v/sass-loader.svg
|
||
[npm-url]: https://npmjs.com/package/sass-loader
|
||
[node]: https://img.shields.io/node/v/sass-loader.svg
|
||
[node-url]: https://nodejs.org
|
||
[deps]: https://david-dm.org/webpack-contrib/sass-loader.svg
|
||
[deps-url]: https://david-dm.org/webpack-contrib/sass-loader
|
||
[tests]: https://dev.azure.com/webpack-contrib/sass-loader/_apis/build/status/webpack-contrib.sass-loader?branchName=master
|
||
[tests-url]: https://dev.azure.com/webpack-contrib/sass-loader/_build/latest?definitionId=21&branchName=master
|
||
[cover]: https://codecov.io/gh/webpack-contrib/sass-loader/branch/master/graph/badge.svg
|
||
[cover-url]: https://codecov.io/gh/webpack-contrib/sass-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
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