Introduction to css-loader

The css-loader is a powerful module for Webpack that enables the loading and bundling of CSS files within JavaScript applications. It transforms @import and url() directives into require() statements, making it easier to manage styles in modern web development.

Basic Usage

To use css-loader, you need to install it using npm or yarn:

npm install css-loader --save-dev

yarn add css-loader --dev

Webpack Configuration

Once installed, you can configure it in your Webpack config:

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/,
        use: ['style-loader', 'css-loader'],
      },
    ],
  },
}; 

API Options

The css-loader comes with several options to customize its behavior:

1. importLoaders

This option allows you to configure the number of loaders applied before css-loader.

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          'style-loader',
          {
            loader: 'css-loader',
            options: { importLoaders: 1 },
          },
          'postcss-loader',
        ],
      },
    ],
  },
}; 

2. modules

Enables CSS Modules, a popular feature that scopes CSS by automatically assigning unique class names.

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          'style-loader',
          {
            loader: 'css-loader',
            options: { modules: true },
          },
        ],
      },
    ],
  },
}; 

3. sourceMap

Generates source maps for better debugging capabilities.

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          'style-loader',
          {
            loader: 'css-loader',
            options: { sourceMap: true },
          },
        ],
      },
    ],
  },
}; 

App Example

Here’s a simple example of a Webpack configuration with css-loader:

// webpack.config.js
const path = require('path');
module.exports = {
  entry: './src/index.js',
  output: {
    filename: 'bundle.js',
    path: path.resolve(__dirname, 'dist'),
  },
  module: {
    rules: [
      {
        test: /\.css$/,
        use: ['style-loader', 'css-loader'],
      },
    ],
  },
};
// src/index.js import './style.css';
const element = document.createElement('div'); element.innerHTML = 'Hello, world!'; document.body.appendChild(element);
// src/style.css body {
  background-color: #222;
  color: #fff;
} 

With this configuration, webpack will process CSS files, enabling you to focus on building your app without worrying about managing stylesheets manually.

For more detailed options, visit the official css-loader documentation.

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