css-loader VS css-modules

@fbem/css-loader is very similar to css-loader (and actually a fork of it) and has almost the same set of options and functionality. You can even use it with different style preprocessors by simply chaining loaders together in webpack config. But be sure to pick up if you need them 😏.

Css files need a css loader like https://github.com/webpack-contrib/css-loader. In fact I see you already have 2 css loaders in your normal webpack config. the server config needs those too. Your fronted build and server build will be very similar in that regard.

React comes by default with css module support via https://github.com/webpack-contrib/css-loader, which is stable and not deprecated. (Note that this entirely independent of react)

I have enabled CSS modules within webpack.config in my React application so that I can locally scope CSS files to individual components. I'm also trying to use the TabView component from PrimeReact. When I do so the themes from PrimeReact are not applied. If I create a separate project and do not enable CSS modules the themes apply correctly.

this is technically a feature of css-loader and not of nextjs, next just supports it ootb through their webpack config. iirc its this option you need to customize

const config = { mode: isProdBuild ? 'production' : 'development', devtool: isProdBuild ? 'source-map' : 'cheap-module-eval-source-map', entry: { app: `${SRC_DIR}/index.js`, }, optimization: { minimize: isProdBuild, sideEffects: true, }, context: SRC_DIR, stats: { colors: true, hash: true, timings: true, assets: true, chunks: false, chunkModules: false, modules: false, children: false, warnings: true, }, module: { rules: [ transpileJavaScriptRule(mode), loadWebWorkersRule, loadShadersRule, ], }, resolve: { // Which directories to search when resolving modules modules: [ // Modules specific to this package path.resolve(__dirname, '../node_modules'), // Hoisted Yarn Workspace Modules path.resolve(__dirname, '../../../node_modules'), SRC_DIR, ], // Attempt to resolve these extensions in order. extensions: ['.js', '.jsx', '.json', '*'], // symlinked resources are resolved to their real path, not their symlinked location symlinks: true, }, plugins: [ new webpack.DefinePlugin({ /* Application */ 'process.env.NODE_ENV': JSON.stringify(process.env.NODE_ENV), 'process.env.DEBUG': JSON.stringify(process.env.DEBUG), 'process.env.APP_CONFIG': JSON.stringify(process.env.APP_CONFIG || ''), 'process.env.PUBLIC_URL': JSON.stringify(process.env.PUBLIC_URL || ''), 'process.env.VERSION_NUMBER': JSON.stringify(PACKAGE.version || ''), 'process.env.BUILD_NUM': JSON.stringify(BUILD_NUM), /* i18n */ 'process.env.USE_LOCIZE': JSON.stringify(process.env.USE_LOCIZE || ''), 'process.env.LOCIZE_PROJECTID': JSON.stringify(process.env.LOCIZE_PROJECTID || ''), 'process.env.LOCIZE_API_KEY': JSON.stringify(process.env.LOCIZE_API_KEY || ''), /* XNAT dev */ 'process.env.XNAT_PROXY': JSON.stringify(process.env.XNAT_PROXY || ''), 'process.env.XNAT_DOMAIN': JSON.stringify(process.env.XNAT_DOMAIN || ''), 'process.env.XNAT_USERNAME': JSON.stringify(process.env.XNAT_USERNAME || ''), 'process.env.XNAT_PASSWORD': JSON.stringify(process.env.XNAT_PASSWORD || ''), }), ], // // Fix: https://github.com/webpack-contrib/css-loader/issues/447#issuecomment-285598881 // // For issue in cornerstone-wado-image-loader // node: { // fs: 'empty', // }, };

One possible non-JSS solution is css-modules supported in css-loader. That requires some setup which may get convoluted if you need CSS preprocessors or SSR.

✨ css loader 💥 jss 🌟 csjs ☄️ aphrodite

Before we start, you should have a minimum knowledge of webpack, you should have css-loader. Along this article, I use nuxt for example, but you can use React or Angular.

The above should work in Create React App out of the box. If you are rolling your own Webpack configuration (may God have mercy on your soul), you'll need to configure modules with a compileType of icss:

One aspect of CSS modules that I truly appreciate is its ability to compress class names into very short hashes. This feature allows me to keep my CSS selectors as long and descriptive as needed, while still compressing them into concise three or four character hashes. It aligns with my rule for CSS: selectors should be written for human readability, but compressed for machine efficiency.

Use methodologies such as BEM, and technologies including CSS modules, CSS-in-JS, and Shadow DOM to isolate the styles of each micro-application and prevent conflicts, thus ensuring reliable encapsulation and modularity.

For many years, Culture Amp took the second option, and distributed shared components without compiled CSS. This meant that every app that consumed shared components needed to include the necessary CSS build tooling – at that time CSS Modules and node-sass – with a compatible version and configuration. This was relatively easy to set up, but over time proved difficult to maintain. When node-sass was deprecated in favour of (the much faster but slightly incompatible) Dart Sass, this demanded a difficult lock-step migration across all those codebases, which we have yet to achieve. And as new applications have switched to Tailwind for their own styles, they've had to continue to maintain those old build tools in parallel for the shared components' styles.

So CSS modules are a form of 3rd-party CSS-in-JS, where what you import are the class names, which are then usually obfuscated etc at compile time, and all the actual style declarations are (usually) compiled into a single css file or tag as part of the bundling process. You can read the og docs on'em here, and you've probably seen'em used in React like:

import styles from "./styles.css";

function Example(){
    return (
        

            Hello
        
    );
}

They predate the ability to import non-js files in vanilla by a good while, and rely on the compile process to translate your .css files into .js files that can be imported using whichever loader you use in your bundler.

Import assertions are a vanilla way to import non-js files by telling the browser how to import them; assert { type: "css" } says to treat the file as CSS and create a CSSStyleSheet, assert { type: "json" } says to treat the file as JSON and create a JSON object - and hopefully assert { type: "html" } will hopefully arrive soon and create a #document-fragment or something similar.

Hope that clears it up!

Extensions of CSS: for example, Sass, Less, Tailwind, CSS Modules, to make stuff look a certain way on your own.

The components are styled with CSS modules. When building the library, these styles will get transformed to normal CSS style sheets. This means that the consuming application will not even be required to support CSS modules. (In the future I want to extend this tutorial to use vanilla-extract instead.)

NextJS comes with built-in support for CSS Modules which allows you to scope your styles locally in individual components without worrying about name collisions or messing up other parts of the codebase.

CSS modules are not to be confused with mixins, as they serve the opposite purpose. While mixins are components or functions to be reused globally, modules are style sheets with a local scope used in a similar way as styled components in React.

CSS Modules CSS Modules is a pre-processing step: by default, styles are scoped locally to the current component, and the transpiler ensures no conflicts.