sass-loader
Advanced tools
The sass-loader npm package is a loader for webpack that allows you to preprocess .scss or .sass files to standard CSS. It uses the Sass compiler to convert Sass code into CSS, and then webpack can bundle the resulting CSS into your final build.
Compiling Sass/SCSS to CSS
This webpack configuration snippet demonstrates how to set up sass-loader in conjunction with css-loader and style-loader to process .scss files.
module.exports = {
module: {
rules: [
{
test: /\.scss$/,
use: [
'style-loader',
'css-loader',
'sass-loader'
]
}
]
}
};Source Maps
This code enables source maps for easier debugging of Sass files. It configures sass-loader to generate source maps so that the browser dev tools can display the original Sass code instead of the compiled CSS.
module.exports = {
module: {
rules: [
{
test: /\.scss$/,
use: [
'style-loader',
{
loader: 'css-loader',
options: { sourceMap: true }
},
{
loader: 'sass-loader',
options: { sourceMap: true }
}
]
}
]
}
};Custom Functions
This example shows how to add custom functions to the Sass compilation process. The custom 'pow' function can be used within Sass files to compute powers.
const sass = require('sass');
module.exports = {
module: {
rules: [
{
test: /\.scss$/,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
sassOptions: {
functions: {
'pow($base, $exponent)': function(base, exponent) {
return new sass.types.Number(Math.pow(base.getValue(), exponent.getValue()));
}
}
}
}
}
]
}
]
}
};node-sass is a library that provides binding for Node.js to the Sass compiler. It allows you to natively compile .scss files to css at incredible speed. However, node-sass is deprecated in favor of Dart Sass.
postcss-loader is a tool that uses PostCSS to process CSS with JavaScript plugins. It can be used for tasks such as autoprefixing, linting, and more. While sass-loader focuses on compiling Sass, postcss-loader is more about post-processing CSS.
less-loader is similar to sass-loader but for Less, which is another preprocessor language that extends the capabilities of CSS. It's a loader for webpack that compiles Less to CSS.
stylus-loader enables webpack to compile Stylus files to CSS. Stylus is another CSS preprocessor scripting language, offering similar features to Sass/SCSS.
npm install sass-loader node-sass webpack --save-dev
The sass-loader requires node-sass and webpack
as peerDependency. Thus you are able to specify the required versions accurately.
var css = require("!raw!sass!./file.scss");
// returns compiled css code from file.scss, resolves Sass imports
var css = require("!css!sass!./file.scss");
// returns compiled css code from file.scss, resolves Sass and CSS imports and url(...)s
Use in tandem with the style-loader and css-loader to add the css rules to your document:
require("!style!css!sass!./file.scss");
Please note: If you encounter module errors complaining about a missing style or css module, make sure you have installed all required loaders via npm.
It's recommended to adjust your webpack.config so style!css!sass! is applied automatically on all files ending on .scss:
module.exports = {
...
module: {
loaders: [
{
test: /\.scss$/,
loaders: ["style", "css", "sass"]
}
]
}
};
Then you only need to write: require("./file.scss").
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$/,
loaders: ["style", "css", "sass"]
}
]
},
sassLoader: {
includePaths: [path.resolve(__dirname, "./some-folder")]
}
};
Passing your options as query parameters is also supported, but can get confusing if you need to set a lot of options.
If you need to define two different loader configs, you can also change the config's property name via sass?config=otherSassLoaderConfig:
module.exports = {
...
module: {
loaders: [
{
test: /\.scss$/,
loaders: ["style", "css", "sass?config=otherSassLoaderConfig"]
}
]
},
otherSassLoaderConfig: {
...
}
};
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/less/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";
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.ENV + ";"
}
};
url(...)Since Sass/libsass does not provide url rewriting, all linked assets must be relative to the output.
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:
$icon-font-path. Check out this working bootstrap example.Bundling CSS with webpack has some nice advantages like referencing images and fonts with hashed urls or hot module replacement in development. In production, on the other hand, it's not a good idea to apply your stylesheets depending on JS execution. Rendering may be delayed or even a FOUC might be visible. Thus it's often still better to have them as separate files in your final production build.
There are two possibilties to extract a stylesheet from the bundle:
To enable CSS Source maps, you'll need to pass the sourceMap-option to the sass- and the css-loader. Your webpack.config.js should look like this:
module.exports = {
...
devtool: "source-map", // or "inline-source-map"
module: {
loaders: [
{
test: /\.scss$/,
loaders: ["style", "css?sourceMap", "sass?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.
FAQs
Sass loader for webpack
The npm package sass-loader receives a total of 2,550,588 weekly downloads. As such, sass-loader popularity was classified as popular.
We found that sass-loader demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 3 open source maintainers collaborating on the project.
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