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把之前百度云的代码移植过来
2024-01-03 07:23:47 +00:00
<div align="center">
<img height="100"
src="https://worldvectorlogo.com/logos/sass-1.svg">
<a href="https://github.com/webpack/webpack">
<img width="200" height="200"
src="https://webpack.js.org/assets/icon-square-big.svg">
</a>
</div>
[![npm][npm]][npm-url]
[![node][node]][node-url]
[![deps][deps]][deps-url]
[![tests][tests]][tests-url]
[![coverage][cover]][cover-url]
[![chat][chat]][chat-url]
[![size][size]][size-url]
# sass-loader
Loads a Sass/SCSS file and compiles it to CSS.
## Getting Started
To begin, you'll need to install `sass-loader`:
```console
npm install sass-loader node-sass webpack --save-dev
```
The 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 you can find below).
This allows you to control the versions of all your dependencies, and to choose which Sass implementation to use.
- [node sass](https://github.com/sass/node-sass)
- [dart sass](http://sass-lang.com/dart-sass)
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.
Then add the loader to your `webpack` config. For example:
**file.js**
```js
import style from './style.scss';
```
**file.scss**
```scss
$body-color: red;
body {
color: $body-color;
}
```
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/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.
### Resolving `import` at-rules
The 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:
```css
@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";`
### Problems with `url(...)`
Since sass implementations don't provide [url rewriting](https://github.com/sass/libsass/issues/532), all linked assets must be relative to the output.
- If you pass the generated CSS on to the css-loader, all urls must be relative to the entry-file (e.g. `main.scss`).
- If you're just generating CSS without passing it to the css-loader, it must be relative to your web root.
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:
- 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.
- Library authors usually provide a variable to modify the asset path. [bootstrap-sass](https://github.com/twbs/bootstrap-sass) for example has an `$icon-font-path`.
## Options
By default all options passed to loader also passed to to [Node Sass](https://github.com/sass/node-sass) or [Dart Sass](http://sass-lang.com/dart-sass)
> ℹ️ The `indentedSyntax` option has `true` value for the `sass` extension.
> ℹ️ Options such as `file` and `outFile` are unavailable.
> ℹ️ Only the "expanded" and "compressed" values of outputStyle are supported for `dart-sass`.
> ℹ We recommend don't use `sourceMapContents`, `sourceMapEmbed`, `sourceMapRoot` options because loader automatically setup this options.
There is a slight difference between the `node-sass` and `sass` options. We recommend look documentation before used them:
- [the Node Sass documentation](https://github.com/sass/node-sass/#options) for all available `node-sass` options.
- [the Dart Sass documentation](https://github.com/sass/dart-sass#javascript-api) for all available `sass` options.
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/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**
```json
{
"devDependencies": {
"sass-loader": "^7.2.0",
"sass": "^1.22.10"
}
}
```
Example where the `sass-loader` loader uses the `node-sass` implementation:
**package.json**
```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:
```js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
// Prefer `dart-sass`
implementation: require('sass'),
},
},
],
},
],
},
};
```
Note that when using `sass` (`Dart Sass`), **synchronous compilation is twice as fast as asynchronous compilation** by default, due to the overhead of asynchronous callbacks.
To avoid this overhead, you can use the [fibers](https://www.npmjs.com/package/fibers) package to call asynchronous importers from the synchronous code path.
To enable this, pass the `Fiber` class to the `fiber` option:
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/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`
```js
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`
```js
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 '$value: 200px;';
},
},
},
],
},
],
},
};
```
### `sourceMap`
Type: `Boolean`
Default: `false`
Enables/Disables generation of source maps.
They are not enabled by default because they expose a runtime overhead and increase in bundle size (JS source maps do not).
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/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 is `node-sass` bug), to avoid try to update node-sass to latest version or you can try to set the `outputStyle` option to `compressed` 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`](https://github.com/sass/node-sass#importer--v200---experimental)).
**webpack.config.js**
```js
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/i,
use: [
'style-loader',
'css-loader',
{
loader: 'sass-loader',
options: {
webpackImporter: false,
},
},
],
},
],
},
};
```
## Examples
### Extracts CSS into separate files
For production builds it's recommended to extract the CSS from your bundle being able to use parallel loading of CSS/JS resources later on.
There are two possibilities to extract a style sheet from the bundle:
- [mini-css-extract-plugin](https://github.com/webpack-contrib/mini-css-extract-plugin) (use this, when using webpack 4 configuration. Works in all use-cases)
- [extract-loader](https://github.com/peerigon/extract-loader) (simpler, but specialized on the css-loader's output)
**webpack.config.js**
```js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
module.exports = {
module: {
rules: [
{
test: /\.s[ac]ss$/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',
}),
],
};
```
### Source maps
To enable CSS source maps, you'll need to pass the `sourceMap` option to the sass-loader _and_ the css-loader.
**webpack.config.js**
```javascript
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](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.
## Contributing
Please take a moment to read our contributing guidelines if you haven't yet done so.
[CONTRIBUTING](./.github/CONTRIBUTING.md)
## License
[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