Sass loader for webpack

Install

npm install sass-loader node-sass webpack --save-dev

The sass-loader requires node-sass and webpack as peerDependency. Thus you are able to specify the required versions accurately.

Usage

Documentation: Using loaders

var css = require("!raw-loader!sass-loader!./file.scss");
// returns compiled css code from file.scss, resolves Sass imports
var css = require("!css-loader!sass-loader!./file.scss");
// returns compiled css code from file.scss, resolves Sass and CSS imports and url(...)s

Use in tandem with the style-loader and css-loader to add the css rules to your document:

require("!style-loader!css-loader!sass-loader!./file.scss");

Please note: If you encounter module errors complaining about a missing style or css module, make sure you have installed all required loaders via npm.

Apply via webpack config

It's recommended to adjust your webpack.config so style-loader!css-loader!sass-loader! is applied automatically on all files ending on .scss:

module.exports = {
  ...
  module: {
    loaders: [
      {
        test: /\.scss$/,
        loaders: ["style-loader", "css-loader", "sass-loader"]
      }
    ]
  }
};

Then you only need to write: require("./file.scss").

Sass options

You can pass options to node-sass by defining a sassLoader property on your webpack.config.js. See node-sass for all available Sass options.

module.exports = {
  ...
  module: {
    loaders: [
      {
        test: /\.scss$/,
        loaders: ["style-loader", "css-loader", "sass-loader"]
      }
    ]
  },
  sassLoader: {
    includePaths: [path.resolve(__dirname, "./some-folder")]
  }
};

Passing your options as query parameters is also supported, but can get confusing if you need to set a lot of options.

If you need to define two different loader configs, you can also change the config's property name via sass-loader?config=otherSassLoaderConfig:

module.exports = {
  ...
  module: {
    loaders: [
      {
        test: /\.scss$/,
        loaders: ["style-loader", "css-loader", "sass-loader?config=otherSassLoaderConfig"]
      }
    ]
  },
  otherSassLoaderConfig: {
    ...
  }
};

Imports

webpack provides an advanced mechanism to resolve files. The sass-loader uses node-sass' 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:

@import "~bootstrap/css/bootstrap";

Alternatively, for bootstrap-sass:

@import "~bootstrap-sass/assets/stylesheets/bootstrap";

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";

Environment variables

If you want to prepend Sass code before the actual entry file, you can simply 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:

module.exports = {
  ...
  sassLoader: {
    data: "$env: " + process.env.NODE_ENV + ";"
  }
};

Problems with url(...)

Since Sass/libsass does not provide url rewriting, all linked assets must be relative to the output.

• If you're just generating CSS without passing it to the css-loader, it must be relative to your web root.
• If you pass the generated CSS on to the css-loader, all urls must be relative to the entry-file (e.g. main.scss).

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:

• Add the missing url rewriting using the resolve-url-loader. Place it directly after the sass-loader in the loader chain.
• Library authors usually provide a variable to modify the asset path. bootstrap-sass for example has an $icon-font-path. Check out this working bootstrap example.

Extracting stylesheets

Bundling CSS with webpack has some nice advantages like referencing images and fonts with hashed urls or hot module replacement in development. In production, on the other hand, it's not a good idea to apply your stylesheets depending on JS execution. Rendering may be delayed or even a FOUC might be visible. Thus it's often still better to have them as separate files in your final production build.

There are two possibilties to extract a stylesheet from the bundle:

• extract-loader (simpler, but specialized on the css-loader's output)
• extract-text-webpack-plugin (more complex, but works in all use-cases)

Source maps

To enable CSS Source maps, you'll need to pass the sourceMap option to the sass and the css-loader. Your webpack.config.js should look like this:

module.exports = {
    ...
    devtool: "source-map", // or "inline-source-map"
    module: {
        loaders: [
            {
                test: /\.scss$/,
                loaders: ["style-loader", "css-loader?sourceMap", "sass-loader?sourceMap"]
            }
        ]
    }
};

If you want to edit the original Sass files inside Chrome, there's a good blog post. Checkout test/sourceMap for a running example.

License

MIT (http://www.opensource.org/licenses/mit-license.php)