css-modules-require-hook

What is css-modules-require-hook?

The css-modules-require-hook package is a tool that allows you to use CSS Modules in Node.js by transforming CSS files into JavaScript objects. This is particularly useful for server-side rendering (SSR) and testing environments where you need to handle CSS files in a Node.js context.

What are css-modules-require-hook's main functionalities?

Basic Setup

This feature allows you to set up the css-modules-require-hook with a custom naming pattern for the generated CSS class names. The code sample demonstrates how to configure the hook and require a CSS file, which will be transformed into a JavaScript object.

const hook = require('css-modules-require-hook');

hook({
  generateScopedName: '[name]__[local]___[hash:base64:5]'
});

const styles = require('./styles.css');
console.log(styles);

Custom Preprocessor

This feature allows you to use a custom preprocessor like Sass. The code sample shows how to configure the hook to preprocess SCSS files using node-sass before transforming them into JavaScript objects.

const hook = require('css-modules-require-hook');
const sass = require('node-sass');

hook({
  extensions: ['.scss'],
  preprocessCss: (data, filename) => {
    return sass.renderSync({
      data,
      file: filename
    }).css;
  }
});

const styles = require('./styles.scss');
console.log(styles);

Custom CamelCase

This feature enables the conversion of CSS class names to camelCase in the resulting JavaScript object. The code sample demonstrates how to configure the hook to use camelCase and access the class names in camelCase format.

const hook = require('css-modules-require-hook');

hook({
  camelCase: true
});

const styles = require('./styles.css');
console.log(styles);
console.log(styles.someClassName); // Access class names in camelCase

Other packages similar to css-modules-require-hook

babel-plugin-react-css-modules

babel-plugin-react-css-modules is a Babel plugin that allows you to use CSS Modules in React components with a more seamless integration. Unlike css-modules-require-hook, which is used in a Node.js context, this plugin is specifically designed for use with Babel and React.

postcss-modules

postcss-modules is a PostCSS plugin that enables the use of CSS Modules. It provides more flexibility and can be integrated into a broader PostCSS setup, making it suitable for build processes that already use PostCSS. Unlike css-modules-require-hook, it is not limited to Node.js environments.

css-modules-loader-core

css-modules-loader-core is a low-level library for loading and processing CSS Modules. It provides the core functionality needed to implement CSS Modules in various environments. While css-modules-require-hook is a higher-level tool for Node.js, css-modules-loader-core offers more granular control and can be used to build custom solutions.

README

css-modules-require-hook

The require hook compiles CSS Modules in runtime. This is similar to Babel's babel/register. See the example: demo.

What is CSS Modules

A CSS Module is a CSS file in which all class names and animation names are scoped locally by default. Learn more in the article CSS Modules - Welcome to the Future by Glen Maddern.

Features

Compiling in runtime, universal usage.

Requirements

To use this tool we require Node.js v0.12.x (or higher).

Installation

$ npm i css-modules-require-hook

Usage

Now, there are two ways to attach hook: manually or using preset file.

The first one allows you to pass options manually after module was required. Example:

const hook = require('css-modules-require-hook');

hook({
  generateScopedName: '[name]__[local]___[hash:base64:5]',
});

// const styles = require('./icon.css');

The second one allows you to move options to the separate file cmrh.conf.js. Config file should be located in the same directory where executor is or in its ancestor directories. In that case hook will be attached right after the css-modules-require-hook/preset module will be required. Example:

// cmrh.conf.js
module.exports = {
  generateScopedName: '[name]__[local]___[hash:base64:5]',
};

require('css-modules-require-hook/preset');

// const styles = require('./icon.css');

Development mode

Usually, Node.js caches all the require calls by default. In order to invalidate cache for the purpose of development you should set the environment variable NODE_ENV to development. For example:

$ NODE_ENV=development node server.js

Still you can use devMode option (see below) to override behavior which is imposed by environment variable.

Adding custom PostCSS plugins

var hook = require('css-modules-require-hook');
var cssnext = require('cssnext');

hook({
  prepend: [
    // adding CSS Next plugin
    cssnext(),
  ],
});

Specify custom pattern to build generic names

var hook = require('css-modules-require-hook');

hook({
  generateScopedName: '[name]__[local]___[hash:base64:5]',
});

Using Stylus as a preprocessor

var hook = require('css-modules-require-hook');
var stylus = require('stylus');

hook({
  extensions: ['.styl'],
  preprocessCss: function (css, filename) {
    return stylus(css)
      .set('filename', filename)
      .render();
  },
});

// var styles = require('./demo.styl');

Tuning (options)

To adjust the require hook you need to provide params to the exported function.

var hook = require('css-modules-require-hook');

hook({
  // append: [],
  // generateScopedName: function () {},
  // or any other options
  // see the list below
});

devMode boolean

Helps you to invalidate cache of all require calls. Usually used for the development purpose. Also overrides behavior, imposed by NODE_ENV environment variable. For example:

hook({
  devMode: false,
});

extensions array

Attach the require hook to additional file extensions (for example ['.scss']).

ignore function|regex|string

Provides possibility to exclude particular files from processing. Supports glob and regular expressions syntax. Also you may provide custom function.

preprocessCss function

In rare cases you may want to precompile styles, before they will be passed to the PostCSS pipeline. You should use synchronous transformations, since require function is synchronous.

hook({
  /**
   * @param  {string} css
   * @param  {string} filepath Absolute path to the file
   * @return {string}
   */
  preprocessCss: function (css, filepath) {
    return css;
  }
});

processCss function

In rare cases you may want to get compiled styles in runtime, so providing this option helps.

hook({
  /**
   * @param  {string} css
   * @param  {string} filepath Absolute path to the file
   */
  processCss: function (css, filepath) { /* */ }
});

processorOpts object

Provides possibility to pass custom options to the LazyResult instance. It can be usefull if you want to set the custom parser, for example: postcss-less.

const hook = require('css-modules-require-hook');
const lessParser = require('postcss-less').parse;

hook({
  extensions: '.less',
  processorOpts: {parser: lessParser},
});

camelCase boolean

Camelizes exported class names. Similar to css-loader?camelCase.

append array

Appends custom plugins to the end of the PostCSS pipeline. Since the require function is synchronous, you should provide synchronous plugins only.

prepend array

Prepends custom plugins to the beginning of the PostCSS pipeline. Since the require function is synchronous, you should provide synchronous plugins only.

use array

Provides the full list of PostCSS plugins to the pipeline. Providing this cancels append, prepend, createImportedName, generateScopedName options. Synchronous plugins only.

createImportedName function

Short alias for the postcss-modules-extract-imports plugin's createImportedName option.

generateScopedName string|function

Short alias for the postcss-modules-scope plugin's option. Helps you to specify the custom way to build generic names for the class selectors. You may also use a string pattern similar to the webpack's css-loader.

hook({
  generateScopedName: '[name]__[local]___[hash:base64:5]'
});

or

hook({
  /**
   * @param  {string} name     Usually a class name
   * @param  {string} filepath
   * @param  {string} css
   * @return {string}
   */
  generateScopedName: function (name, filepath, css) {
    return name;
  }
});

hashPrefix string

Short alias for the generic-names helper option. Provides additional hash uniqueness. Might be useful for projects with several stylesheets sharing a same name.

mode string

Short alias for the postcss-modules-local-by-default plugin's option.

rootDir string

Provides absolute path to the project directory. Providing this will result in better generated class names. It can be obligatory, if you run require hook and build tools (like css-modulesify) from different working directories.

Debugging

debug package is used for debugging. So to turn it on simply specify the DEBUG environment variable:

• DEBUG=css-modules:fetch — to see resolved paths to the files.
• DEBUG=css-modules:preset — to see whether config was found or not.
• DEBUG=css-modules:setup — to see the new options list.
• DEBUG=css-modules:* — to see everything.

Links

• Electron support: css-modules-electron

License

The MIT License