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Extract CSS from chunks into multiple stylesheets + HMR
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faceyspacey/extract-css-chunks-webpack-plugin
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If you like our work, check out our Redux-based routerredux-first-router or its sucessor which,Rudy
HEADLINES (May 2018): Now Independently supports Webpack 4:Yep that's right. The universal family is now fully Webpack 4. Thank you to all our users for your loyalty and patience! If you love Universal, then you are gonna fall head over heels when we bring out the main course!
So... why did we rebuildextract-css-chunks-webpack-plugin? What does it offer?
It's got all the goodness ofmini-css-extract-plugin but with 2 gleaming, sought after benefits.
Compared to the existing loaders, we are offering a single solution as opposed to needing to depend on multiple loaders to cater for different features:
- HMR: It also has first-class support forHot Module Replacement across ALL those css files/chunks!!!
- cacheable stylesheets
- smallest total bytes sent compared to "render-path" css-in-js solutions that include your CSS definitions in JS
- Faster than the V2!
- Async loading
- No duplicate compilation (performance)
- Easier to use
- Specific to CSS
- SSR Friendly development build, focused on frontend DX
- Works seamlessly with the Universal family
- Works fantastically as a standalone style loader (You can use it for any webpack project! with no extra dependencies!)
- Async styles do not render block webkit browsers, if you use the
insertoption
Additionally, if you are already a user of the universal family -- we will be waving goodbye to the mandatorywindow.__CSS_CHUNKS__.
The functionality is still available to you via chunk flushing, and it can come in super handy when needing to easily resolve style assets as urls that might need to be passed to a third party.
webpack.config.js
constExtractCssChunks=require('extract-css-chunks-webpack-plugin');module.exports={plugins:[newExtractCssChunks()],module:{rules:[{test:/\.css$/i,use:[ExtractCssChunks.loader,'css-loader'],},],},};
Type:String|FunctionDefault: thepublicPath inwebpackOptions.output
Specifies a custom public path for the target file(s).
webpack.config.js
constExtractCssChunks=require('extract-css-chunks-webpack-plugin');module.exports={plugins:[newExtractCssChunks({// Options similar to the same options in webpackOptions.output// both options are optionalfilename:'[name].css',chunkFilename:'[id].css',}),],module:{rules:[{test:/\.css$/,use:[{loader:ExtractCssChunks.loader,options:{publicPath:'/public/path/to/',},},'css-loader',],},],},};
webpack.config.js
constExtractCssChunks=require('extract-css-chunks-webpack-plugin');module.exports={plugins:[newExtractCssChunks({// Options similar to the same options in webpackOptions.output// both options are optionalfilename:'[name].css',chunkFilename:'[id].css',}),],module:{rules:[{test:/\.css$/,use:[{loader:ExtractCssChunks.loader,options:{publicPath:(resourcePath,context)=>{returnpath.relative(path.dirname(resourcePath),context)+'/';},},},'css-loader',],},],},};
Type:BooleanDefault:false
By default,extract-css-chunks-webpack-plugin generates JS modules that use the CommonJS modules syntax.There are some cases in which using ES modules is beneficial, like in the case ofmodule concatenation andtree shaking.
You can enable a ES module syntax using:
webpack.config.js
constExtractCssChunks=require('extract-css-chunks-webpack-plugin');module.exports={plugins:[newExtractCssChunks()],module:{rules:[{test:/\.css$/i,use:[{loader:ExtractCssChunks.loader,options:{esModule:true,},},'css-loader',],},],},};
webpack.config.js
constExtractCssChunks=require('extract-css-chunks-webpack-plugin');module.exports={plugins:[newExtractCssChunks({// Options similar to the same options in webpackOptions.output// all options are optionalfilename:'[name].css',chunkFilename:'[id].css',ignoreOrder:false,// Enable to remove warnings about conflicting order}),],module:{rules:[{test:/\.css$/,use:[{loader:ExtractCssChunks.loader,options:{// you can specify a publicPath here// by default it uses publicPath in webpackOptions.outputpublicPath:'../',hmr:process.env.NODE_ENV==='development',},},'css-loader',],},],},};
webpack.config.js
constExtractCssChunks=require('extract-css-chunks-webpack-plugin');module.exports={plugins:[newExtractCssChunks({// Options similar to the same options in webpackOptions.output// both options are optionalfilename:'[name].css',chunkFilename:'[id].css',}),],module:{rules:[{test:/\.css$/,use:[{loader:ExtractCssChunks.loader,options:{publicPath:(resourcePath,context)=>{// publicPath is the relative path of the resource to the context// e.g. for ./css/admin/main.css the publicPath will be ../../// while for ./css/main.css the publicPath will be ../returnpath.relative(path.dirname(resourcePath),context)+'/';},},},'css-loader',],},],},};
This plugin should be used only onproduction builds withoutstyle-loader in the loaders chain, especially if you want to have HMR indevelopment.
Here is an example to have both HMR indevelopment and your styles extracted in a file forproduction builds.
(Loaders options left out for clarity, adapt accordingly to your needs.)
webpack.config.js
constExtractCssChunks=require('extract-css-chunks-webpack-plugin');constdevMode=process.env.NODE_ENV!=='production';module.exports={plugins:[newExtractCssChunks({// Options similar to the same options in webpackOptions.output// both options are optionalfilename:devMode ?'[name].css' :'[name].[hash].css',chunkFilename:devMode ?'[id].css' :'[id].[hash].css',}),],module:{rules:[{test:/\.(sa|sc|c)ss$/,use:[{loader:ExtractCssChunks.loader,options:{hmr:process.env.NODE_ENV==='development',},},'css-loader','postcss-loader','sass-loader',],},],},};
Theextract-css-chunks-webpack-plugin supports hot reloading of actual css files in development.Some options are provided to enable HMR of both standard stylesheets and locally scoped CSS or CSS modules.Below is an example configuration ofextract-css-chunks for HMR use with CSS modules.
While we attempt to hmr css-modules. It is not easy to perform when code-splitting with custom chunk names.reloadAll is an option that should only be enabled if HMR isn't working correctly.The core challenge with css-modules is that when code-split, the chunk ids can and do end up different compared to the filename.
webpack.config.js
constExtractCssChunks=require('extract-css-chunks-webpack-plugin');module.exports={plugins:[newExtractCssChunks({// Options similar to the same options in webpackOptions.output// both options are optionalfilename:'[name].css',chunkFilename:'[id].css',}),],module:{rules:[{test:/\.css$/,use:[{loader:ExtractCssChunks.loader,options:{// only enable hot in developmenthmr:process.env.NODE_ENV==='development',// if hmr does not work, this is a forceful method.reloadAll:true,},},'css-loader',],},],},};
To minify the output, use a plugin likeoptimize-css-assets-webpack-plugin.Settingoptimization.minimizer overrides the defaults provided by webpack, so make sure to also specify a JS minimizer:
webpack.config.js
constTerserJSPlugin=require('terser-webpack-plugin');constExtractCssChunks=require('extract-css-chunks-webpack-plugin');constOptimizeCSSAssetsPlugin=require('optimize-css-assets-webpack-plugin');module.exports={optimization:{minimizer:[newTerserJSPlugin({}),newOptimizeCSSAssetsPlugin({})],},plugins:[newExtractCssChunks({filename:'[name].css',chunkFilename:'[id].css',}),],module:{rules:[{test:/\.css$/,use:[ExtractCssChunks.loader,'css-loader'],},],},};
The runtime code detects already added CSS via<link> or<style> tag.This can be useful when injecting CSS on server-side for Server-Side-Rendering.Thehref of the<link> tag has to match the URL that will be used for loading the CSS chunk.Thedata-href attribute can be used for<link> and<style> too.When inlining CSSdata-href must be used.
Similar to whatextract-text-webpack-plugin does, the CSS can be extracted in one CSS file usingoptimization.splitChunks.cacheGroups.
webpack.config.js
constExtractCssChunks=require('extract-css-chunks-webpack-plugin');module.exports={optimization:{splitChunks:{cacheGroups:{styles:{name:'styles',test:/\.css$/,chunks:'all',enforce:true,},},},},plugins:[newExtractCssChunks({filename:'[name].css',}),],module:{rules:[{test:/\.css$/,use:[ExtractCssChunks.loader,'css-loader'],},],},};
You may also extract the CSS based on the webpack entry name.This is especially useful if you import routes dynamically but want to keep your CSS bundled according to entry.This also prevents the CSS duplication issue one had with the ExtractTextPlugin.
constpath=require('path');constExtractCssChunks=require('extract-css-chunks-webpack-plugin');functionrecursiveIssuer(m){if(m.issuer){returnrecursiveIssuer(m.issuer);}elseif(m.name){returnm.name;}else{returnfalse;}}module.exports={entry:{foo:path.resolve(__dirname,'src/foo'),bar:path.resolve(__dirname,'src/bar'),},optimization:{splitChunks:{cacheGroups:{fooStyles:{name:'foo',test:(m,c,entry='foo')=>m.constructor.name==='CssModule'&&recursiveIssuer(m)===entry,chunks:'all',enforce:true,},barStyles:{name:'bar',test:(m,c,entry='bar')=>m.constructor.name==='CssModule'&&recursiveIssuer(m)===entry,chunks:'all',enforce:true,},},},},plugins:[newExtractCssChunks({filename:'[name].css',}),],module:{rules:[{test:/\.css$/,use:[ExtractCssChunks.loader,'css-loader'],},],},};
With themoduleFilename option you can use chunk data to customize the filename. This is particularly useful when dealing with multiple entry points and wanting to get more control out of the filename for a given entry point/chunk. In the example below, we'll usemoduleFilename to output the generated css into a different directory.
webpack.config.js
constExtractCssChunks=require('extract-css-chunks-webpack-plugin');module.exports={plugins:[newExtractCssChunks({moduleFilename:({ name})=>`${name.replace('/js/','/css/')}.css`,}),],module:{rules:[{test:/\.css$/,use:[ExtractCssChunks.loader,'css-loader'],},],},};
For long term caching usefilename: "[contenthash].css". Optionally add[name].
webpack.config.js
constExtractCssChunks=require('extract-css-chunks-webpack-plugin');module.exports={plugins:[newExtractCssChunks({filename:'[name].[contenthash].css',chunkFilename:'[id].[contenthash].css',}),],module:{rules:[{test:/\.css$/,use:[ExtractCssChunks.loader,'css-loader'],},],},};
For projects where css ordering has been mitigated through consistent use of scoping or naming conventions, the css order warnings can be disabled by setting the ignoreOrder flag to true for the plugin.
webpack.config.js
constExtractCssChunks=require('extract-css-chunks-webpack-plugin');module.exports={plugins:[newExtractCssChunks({ignoreOrder:true,}),],module:{rules:[{test:/\.css$/i,use:[ExtractCssChunks.loader,'css-loader'],},],},};
Type:FunctionDefault:head
By default, theextract-css-chunks-plugin appends styles (<link> elements) todocument.head of the currentwindow.
However in some circumstances it might be necessary to have finer control over the append target or even delaylink elements instertion. For example this is the case when you asynchronously load styles for an application that runs inside of an iframe. In such casesinsert can be configured to be a function or a custom selector.
If you target aniframe make sure that the parent document has sufficient access rights to reach into the frame document and append elements to it.
Allows to override default behavior and insert styles at any position.
⚠ Do not forget that this code will run in the browser alongside your application. Since not all browsers support latest ECMA features like
let,const,arrow function expressionand etc we recommend you to use only ECMA 5 features and syntax.
⚠ The
insertfunction is serialized to string and passed to the plugin. This means that it won't have access to the scope of the webpack configuration module.
newExtractCssChunksPlugin({insert:functioninsert(linkTag){constreference=document.querySelector('#some-element');if(reference){reference.parentNode.insertBefore(linkTag,reference);}},});
A new<link> element will be inserted before the element with idsome-element.
If you'd like to extract the media queries from the extracted CSS (so mobile users don't need to load desktop or tablet specific CSS anymore) you should use one of the following plugins:
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Extract CSS from chunks into multiple stylesheets + HMR
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