Product
Introducing Java Support in Socket
We're excited to announce that Socket now supports the Java programming language.
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.
Loads a Sass/SCSS file and compiles it to CSS.
To begin, you'll need to install sass-loader
:
npm install sass-loader node-sass webpack --save-dev
The sass-loader requires you to install either Node Sass or Dart Sass on your own (more documentation you can find below). This allows you to control the versions of all your dependencies, and to choose which Sass implementation to use.
Chain the sass-loader with the css-loader and the style-loader to immediately apply all styles to the DOM or the mini-css-extract-plugin to extract it into a separate file.
Then add the loader to your webpack
config. For example:
file.js
import style from './style.scss';
file.scss
$body-color: red;
body {
color: $body-color;
}
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
// Creates `style` nodes from JS strings
'style-loader',
// Translates CSS into CommonJS
'css-loader',
// Compiles Sass to CSS
'sass-loader',
],
},
],
},
};
And run webpack
via your preferred method.
import
at-rulesThe webpack provides an advanced mechanism to resolve files.
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:
@import '~bootstrap';
It's important to only prepend it with ~
, because ~/
resolves to the home directory.
The 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";
url(...)
Since sass implementations don't provide url rewriting, all linked assets must be relative to the output.
main.scss
).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).
Thankfully there are a two solutions to this problem:
$icon-font-path
.By default all options passed to loader also passed to to Node Sass or Dart Sass
ℹ️ The
indentedSyntax
option hastrue
value for thesass
extension. ℹ️ Options such asfile
andoutFile
are unavailable. ℹ️ Only the "expanded" and "compressed" values of outputStyle are supported fordart-sass
. ℹ We recommend don't usesourceMapContents
,sourceMapEmbed
,sourceMapRoot
options because loader automatically setup this options.
There is a slight difference between the node-sass
and sass
options. We recommend look documentation before used them:
node-sass
options.sass
options.webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
indentWidth: 4,
includePaths: ['absolute/path/a', 'absolute/path/b'],
},
},
],
},
],
},
};
implementation
The special implementation
option determines which implementation of Sass to use.
By default the loader resolve the implementation based on your dependencies.
Just add required implementation to package.json
(node-sass
or sass
package) and install dependencies.
Example where the sass-loader
loader uses the sass
(dart-sass
) implementation:
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"sass": "^1.22.10"
}
}
Example where the sass-loader
loader uses the node-sass
implementation:
package.json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"node-sass": "^4.0.0"
}
}
Beware the situation when node-sass
and sass
was installed, by default the sass-loader
prefers node-sass
, to avoid this situation use the implementation
option.
It takes either node-sass
or sass
(Dart Sass
) module.
For example, to use Dart Sass, you'd pass:
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
// Prefer `dart-sass`
implementation: require('sass'),
},
},
],
},
],
},
};
Note that when using sass
(Dart Sass
), synchronous compilation is twice as fast as asynchronous compilation by default, due to the overhead of asynchronous callbacks.
To avoid this overhead, you can use the fibers package to call asynchronous importers from the synchronous code path.
To enable this, pass the Fiber
class to the fiber
option:
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
implementation: require('sass'),
fiber: require('fibers'),
},
},
],
},
],
},
};
data
Type: String|Function
Default: undefined
Prepends Sass
/SCSS
code before the actual entry file.
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:
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.
String
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
data: '$env: ' + process.env.NODE_ENV + ';',
},
},
],
},
],
},
};
Function
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
data: (loaderContext) => {
// More information about avalaible options https://webpack.js.org/api/loaders/
const { resourcePath, rootContext } = loaderContext;
const relativePath = path.relative(rootContext, resourcePath);
if (relativePath === 'styles/foo.scss') {
return '$value: 100px;';
}
return '$value: 200px;';
},
},
},
],
},
],
},
};
sourceMap
Type: Boolean
Default: false
Enables/Disables generation of source maps.
They are not enabled by default because they expose a runtime overhead and increase in bundle size (JS source maps do not).
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
{
loader: 'css-loader',
options: {
sourceMap: true,
},
},
{
loader: 'sass-loader',
options: {
sourceMap: true,
},
},
],
},
],
},
};
ℹ In some rare case
node-sass
can output invalid source maps (it isnode-sass
bug), to avoid try to update node-sass to latest version or you can try to set theoutputStyle
option tocompressed
value.
webpackImporter
Type: Boolean
Default: true
Allows to disable default webpack
importer.
This can improve performance in some cases. Use it with caution because aliases and @import
at-rules starts with ~
will not work, but you can pass own importer
to solve this (see importer docs
).
webpack.config.js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
webpackImporter: false,
},
},
],
},
],
},
};
For production builds it's recommended to extract the CSS from your bundle being able to use parallel loading of CSS/JS resources later on.
There are two possibilities to extract a style sheet from the bundle:
webpack.config.js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
// fallback to style-loader in development
process.env.NODE_ENV !== 'production'
? 'style-loader'
: MiniCssExtractPlugin.loader,
'css-loader',
'sass-loader',
],
},
],
},
plugins: [
new MiniCssExtractPlugin({
// Options similar to the same options in webpackOptions.output
// both options are optional
filename: '[name].css',
chunkFilename: '[id].css',
}),
],
};
To enable CSS source maps, you'll need to pass the sourceMap
option to the sass-loader and the css-loader.
webpack.config.js
module.exports = {
devtool: 'source-map', // any "source-map"-like devtool is possible
module: {
rules: [
{
test: /\.scss$/,
use: [
'style-loader',
{
loader: 'css-loader',
options: {
sourceMap: true,
},
},
{
loader: 'sass-loader',
options: {
sourceMap: true,
},
},
],
},
],
},
};
If you want to edit the original Sass files inside Chrome, there's a good blog post. Checkout test/sourceMap for a running example.
Please take a moment to read our contributing guidelines if you haven't yet done so.
FAQs
Sass loader for webpack
The npm package sass-loader receives a total of 10,188,321 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.
Did you know?
Socket for GitHub automatically highlights issues in each pull request and monitors the health of all your open source dependencies. Discover the contents of your packages and block harmful activity before you install or update your dependencies.
Product
We're excited to announce that Socket now supports the Java programming language.
Security News
Socket detected a malicious Python package impersonating a popular browser cookie library to steal passwords, screenshots, webcam images, and Discord tokens.
Security News
Deno 2.0 is now available with enhanced package management, full Node.js and npm compatibility, improved performance, and support for major JavaScript frameworks.