Compiles Less to CSS.
npm install --save-dev less-loader less
// webpack.config.jsmoduleexports =...module:rules:test: /\.less$/use:loader: "style-loader" // creates style nodes from JS stringsloader: "css-loader" // translates CSS into CommonJSloader: "less-loader" // compiles Less to CSS;
You can pass any Less specific options to the
less-loader via loader options. See the Less documentation for all available options in dash-case. Since we're passing these options to Less programmatically, you need to pass them in camelCase here:
// webpack.config.jsmoduleexports =...module:rules:test: /\.less$/use:loader: "style-loader"loader: "css-loader"loader: "less-loader" options:strictMath: truenoIeCompat: true;
Unfortunately, Less doesn't map all options 1-by-1 to camelCase. When in doubt, check their executable and search for the dash-case option.
const ExtractTextPlugin = ;const extractLess =filename: "[name].[contenthash].css"disable: processenvNODE_ENV === "development";moduleexports =...module:rules:test: /\.less$/use: extractLessplugins:extractLess;
less-loader 4, you can now choose between Less' builtin resolver and webpack's resolver. By default, webpack's resolver is used.
webpack provides an advanced mechanism to resolve files. The
less-loader applies a Less plugin that passes all queries to the webpack resolver. Thus you can import your Less modules from
node_modules. Just prepend them with a
~ which tells webpack to look up the
It's important to only prepend it with
~/ resolves to the home-directory. webpack needs to distinguish between
~bootstrap, because CSS and Less files have no special syntax for importing relative files. Writing
@import "file" is the same as
Using webpack's resolver, you can import any file type. You just need a loader that exports valid Less code. Often, you will also want to set the
issuer condition to ensure that this rule is only applied on imports originating from Less files:
// webpack.config.jsmoduleexports =...module:rules:test: /\.js$/issuer: /\.less$/use:loader: "js-to-less-loader";
If you specify the
paths option, the
less-loader will not use webpack's resolver. Modules, that can't be resolved in the local folder, will be searched in the given
paths. This is Less' default behavior.
paths should be an array with absolute paths:
// webpack.config.jsmoduleexports =...module:rules:test: /\.less$/use:loader: "style-loader"loader: "css-loader"loader: "less-loader" options:paths:path;
In this case, all webpack features like importing non-Less files or aliasing won't work of course.
In order to use plugins, simply set the
plugins option like this:
// webpack.config.jsconst CleanCSSPlugin = ;moduleexports =...loader: "less-loader" options:plugins:advanced: true...;
Extracting style sheets
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 style sheets 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 possibilities to extract a style sheet from the bundle:
extract-loader(simpler, but specialized on the css-loader's output)
ExtractTextWebpackPlugin(more complex, but works in all use-cases)
To enable CSS source maps, you'll need to pass the
sourceMap option to the
less-loader and the
webpack.config.js should look like this:
moduleexports =...module:rules:test: /\.less$/use:loader: "style-loader"loader: "css-loader" options:sourceMap: trueloader: "less-loader" options:sourceMap: true;
Also checkout the sourceMaps example.
If you want to edit the original Less files inside Chrome, there's a good blog post. The blog post is about Sass but it also works for Less.
CSS modules gotcha