290 lines
11 KiB
Markdown
290 lines
11 KiB
Markdown
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[![npm][npm]][npm-url]
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[![node][node]][node-url]
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[![npm-stats][npm-stats]][npm-url]
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[![deps][deps]][deps-url]
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[![travis][travis]][travis-url]
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[![appveyor][appveyor]][appveyor-url]
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[![coverage][cover]][cover-url]
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[![chat][chat]][chat-url]
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<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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<h1>Sass Loader</h1>
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<p>Loads a Sass/SCSS file and compiles it to CSS.</p>
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</div>
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Use the [css-loader](https://github.com/webpack-contrib/css-loader) or the [raw-loader](https://github.com/webpack-contrib/raw-loader) to turn it into a JS module and the [MiniCssExtractPlugin](https://github.com/webpack-contrib/mini-css-extract-plugin) to extract it into a separate file.
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Looking for the webpack 1 loader? Check out the [archive/webpack-1 branch](https://github.com/webpack-contrib/sass-loader/tree/archive/webpack-1).
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<h2 align="center">Install</h2>
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```bash
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npm install sass-loader node-sass webpack --save-dev
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```
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The sass-loader requires [webpack](https://github.com/webpack) as a
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[`peerDependency`](https://docs.npmjs.com/files/package.json#peerdependencies)
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and it requires you to install either [Node Sass][] or [Dart Sass][] on your
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own. This allows you to control the versions of all your dependencies, and to
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choose which Sass implementation to use.
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[Node Sass]: https://github.com/sass/node-sass
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[Dart Sass]: http://sass-lang.com/dart-sass
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<h2 align="center">Examples</h2>
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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.
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```bash
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npm install style-loader css-loader --save-dev
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```
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```js
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// webpack.config.js
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module.exports = {
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...
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module: {
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rules: [{
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test: /\.scss$/,
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use: [
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"style-loader", // creates style nodes from JS strings
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"css-loader", // translates CSS into CommonJS
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"sass-loader" // compiles Sass to CSS, using Node Sass by default
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]
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}]
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}
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};
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```
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You can also pass options directly to [Node Sass][] or [Dart Sass][]:
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```js
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// webpack.config.js
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module.exports = {
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...
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module: {
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rules: [{
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test: /\.scss$/,
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use: [{
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loader: "style-loader"
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}, {
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loader: "css-loader"
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}, {
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loader: "sass-loader",
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options: {
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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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See [the Node Sass documentation](https://github.com/sass/node-sass/blob/master/README.md#options) for all available Sass options.
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The special `implementation` option determines which implementation of Sass to
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use. It takes either a [Node Sass][] or a [Dart Sass][] module. For example, to
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use Dart Sass, you'd pass:
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```js
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// ...
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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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}
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}
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// ...
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```
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Note that when using Dart Sass, **synchronous compilation is twice as fast as
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asynchronous compilation** by default, due to the overhead of asynchronous
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callbacks. To avoid this overhead, you can use the
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[`fibers`](https://www.npmjs.com/package/fibers) package to call asynchronous
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importers from the synchronous code path. To enable this, pass the `Fiber` class
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to the `fiber` option:
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```js
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// webpack.config.js
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const Fiber = require('fibers');
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module.exports = {
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...
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module: {
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rules: [{
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test: /\.scss$/,
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use: [{
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loader: "style-loader"
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}, {
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loader: "css-loader"
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}, {
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loader: "sass-loader",
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options: {
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implementation: require("sass"),
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fiber: Fiber
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}
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}]
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}]
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}
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};
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```
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### In production
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Usually, it's recommended to extract the style sheets into a dedicated file in production using the [MiniCssExtractPlugin](https://github.com/webpack-contrib/mini-css-extract-plugin). This way your styles are not dependent on JavaScript:
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```js
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const MiniCssExtractPlugin = require("mini-css-extract-plugin");
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module.exports = {
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...
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module: {
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rules: [{
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test: /\.scss$/,
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use: [
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// fallback to style-loader in development
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process.env.NODE_ENV !== 'production' ? 'style-loader' : 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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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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<h2 align="center">Usage</h2>
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### Imports
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webpack provides an [advanced mechanism to resolve files](https://webpack.js.org/concepts/module-resolution/). 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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```css
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@import "~bootstrap/dist/css/bootstrap";
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```
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It's important to only prepend it with `~`, because `~/` resolves to the home directory. webpack needs to distinguish between `bootstrap` and `~bootstrap` because CSS and Sass files have no special syntax for importing relative files. Writing `@import "file"` is the same as `@import "./file";`
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### Problems with `url(...)`
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Since Sass/[libsass](https://github.com/sass/libsass) does not 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're just generating CSS without passing it to the css-loader, it must be relative to your web root.
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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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More likely you will be disrupted by this second issue. It is natural to expect relative references to be resolved against the `.scss` file in which they are specified (like in regular `.css` files). 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 the 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`. Check out [this working bootstrap example](https://github.com/webpack-contrib/sass-loader/tree/master/test/bootstrapSass).
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### Extracting style sheets
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Bundling CSS with webpack has some nice advantages like referencing images and fonts with hashed urls or [hot module replacement](https://webpack.js.org/concepts/hot-module-replacement/) in development. In production, on the other hand, it's not a good idea to apply your style sheets depending on JS execution. Rendering may be delayed or even a [FOUC](https://en.wikipedia.org/wiki/Flash_of_unstyled_content) might be visible. Thus it's often still better to have them as separate files in your final production build.
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There are two possibilities to extract a style sheet from the bundle:
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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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- [extract-text-webpack-plugin](https://github.com/webpack-contrib/extract-text-webpack-plugin) (more complex, but works in all use-cases)
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### 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. Your `webpack.config.js` should look like this:
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```javascript
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module.exports = {
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...
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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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test: /\.scss$/,
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use: [{
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loader: "style-loader"
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}, {
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loader: "css-loader", options: {
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sourceMap: true
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}
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}, {
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loader: "sass-loader", 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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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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### Environment variables
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If you want to prepend Sass code before the actual entry file, you can set the `data` option. In this case, the sass-loader will not override the `data` option but just append the entry's content. This is especially useful when some of your Sass variables depend on the environment:
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```javascript
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{
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loader: "sass-loader",
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options: {
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data: "$env: " + process.env.NODE_ENV + ";"
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}
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}
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```
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**Please note:** 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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<h2 align="center">Maintainers</h2>
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<table>
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<tr>
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<td align="center">
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<a href="https://github.com/jhnns"><img width="150" height="150" src="https://avatars0.githubusercontent.com/u/781746?v=3"></a><br>
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<a href="https://github.com/jhnns">Johannes Ewald</a>
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</td>
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<td align="center">
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<a href="https://github.com/webpack-contrib"><img width="150" height="150" src="https://avatars1.githubusercontent.com/u/1243901?v=3&s=460"></a><br>
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<a href="https://github.com/webpack-contrib">Jorik Tangelder</a>
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</td>
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<td align="center">
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<a href="https://github.com/akiran"><img width="150" height="150" src="https://avatars1.githubusercontent.com/u/3403295?v=3"></a><br>
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<a href="https://github.com/akiran">Kiran</a>
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</td>
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<tr>
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</table>
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<h2 align="center">License</h2>
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[MIT](http://www.opensource.org/licenses/mit-license.php)
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[npm]: https://img.shields.io/npm/v/sass-loader.svg
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[npm-stats]: https://img.shields.io/npm/dm/sass-loader.svg
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[npm-url]: https://npmjs.com/package/sass-loader
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[node]: https://img.shields.io/node/v/sass-loader.svg
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[node-url]: https://nodejs.org
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[deps]: https://david-dm.org/webpack-contrib/sass-loader.svg
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[deps-url]: https://david-dm.org/webpack-contrib/sass-loader
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[travis]: http://img.shields.io/travis/webpack-contrib/sass-loader.svg
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[travis-url]: https://travis-ci.org/webpack-contrib/sass-loader
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[appveyor-url]: https://ci.appveyor.com/project/webpack-contrib/sass-loader/branch/master
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[appveyor]: https://ci.appveyor.com/api/projects/status/rqpy1vaovh20ttxs/branch/master?svg=true
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[cover]: https://codecov.io/gh/webpack-contrib/sass-loader/branch/master/graph/badge.svg
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[cover-url]: https://codecov.io/gh/webpack-contrib/sass-loader
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[chat]: https://badges.gitter.im/webpack/webpack.svg
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[chat-url]: https://gitter.im/webpack/webpack
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