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# Development Tools
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Webpack's development tools provide a comprehensive suite of plugins and features designed to enhance the developer experience. These tools enable hot module replacement, source map generation, progress reporting, file watching, debugging capabilities, and seamless integration with development servers for efficient development workflows.
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## Capabilities
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### Hot Module Replacement
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Hot Module Replacement (HMR) allows modules to be updated at runtime without requiring a full page refresh, dramatically improving development speed and preserving application state.
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```javascript { .api }
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/**
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 * Enables Hot Module Replacement for faster development cycles
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 * @param options - HMR configuration options
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 */
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class HotModuleReplacementPlugin {
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  constructor(options?: {
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    /** Enable multi-step mode for better HMR performance */
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    multiStep?: boolean;
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    /** Timeout for full rebuild in milliseconds */
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    fullBuildTimeout?: number;
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    /** Timeout for HMR requests in milliseconds */
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    requestTimeout?: number;
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  });
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}
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```
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**Usage Examples:**
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```javascript
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const webpack = require("webpack");
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module.exports = {
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  mode: 'development',
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  entry: './src/index.js',
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  devServer: {
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    hot: true,
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    port: 3000
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  },
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  plugins: [
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    new webpack.HotModuleReplacementPlugin({
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      multiStep: true,
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      fullBuildTimeout: 200,
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      requestTimeout: 10000
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    })
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  ]
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};
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// In your application code
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if (module.hot) {
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  module.hot.accept('./component.js', () => {
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    console.log('Component updated!');
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    // Re-render component without page refresh
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  });
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  // Handle disposal
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  module.hot.dispose(() => {
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    // Cleanup before module replacement
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  });
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}
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```
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### Source Map Generation
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Source maps enable debugging of bundled code by mapping minified/transformed code back to original source files with precise line and column information.
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```javascript { .api }
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/**
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 * Generates source maps with fine-grained control over format and output
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 * @param options - Source map generation options
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 */
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class SourceMapDevToolPlugin {
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  constructor(options?: {
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    /** Output filename pattern for source maps */
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    filename?: string | false;
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    /** Include files matching these patterns */
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    include?: string | RegExp | Array<string | RegExp>;
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    /** Exclude files matching these patterns */
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    exclude?: string | RegExp | Array<string | RegExp>;
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    /** Template for module filenames in source maps */
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    moduleFilenameTemplate?: string | ((info: ModuleFilenameTemplateInfo) => string);
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    /** Fallback template when main template fails */
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    fallbackModuleFilenameTemplate?: string | ((info: ModuleFilenameTemplateInfo) => string);
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    /** String appended to source map comment */
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    append?: string | false;
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    /** Include module names in source maps */
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    module?: boolean;
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    /** Include column information in source maps */
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    columns?: boolean;
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    /** Enable line-to-line mode for faster source maps */
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    lineToLine?: boolean | { test?: RegExp | Array<RegExp> };
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    /** Exclude source content from source maps */
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    noSources?: boolean;
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    /** Public path for source map URLs */
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    publicPath?: string;
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    /** Context path for file URLs */
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    fileContext?: string;
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    /** Source root URL prefix */
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    sourceRoot?: string;
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  });
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}
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/**
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 * Fast source maps using eval() for development builds
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 * @param options - Eval source map options
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 */
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class EvalSourceMapDevToolPlugin {
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  constructor(options?: {
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    /** Include files matching these patterns */
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    include?: string | RegExp | Array<string | RegExp>;
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    /** Exclude files matching these patterns */
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    exclude?: string | RegExp | Array<string | RegExp>;
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    /** Template for module filenames */
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    moduleFilenameTemplate?: string | ((info: ModuleFilenameTemplateInfo) => string);
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    /** Include module names */
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    module?: boolean;
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    /** Include column information */
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    columns?: boolean;
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    /** Enable line-to-line mode */
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    lineToLine?: boolean | { test?: RegExp | Array<RegExp> };
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  });
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}
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/**
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 * Wraps modules in eval() statements for better debugging without source maps
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 * @param options - Eval dev tool options
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 */
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class EvalDevToolModulePlugin {
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  constructor(options?: {
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    /** Template for module filenames in eval statements */
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    moduleFilenameTemplate?: string | ((info: ModuleFilenameTemplateInfo) => string);
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    /** Comment template for source URLs */
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    sourceUrlComment?: string;
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  });
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}
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interface ModuleFilenameTemplateInfo {
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  identifier: string;
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  shortIdentifier: string;
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  resource: string;
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  resourcePath: string;
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  absoluteResourcePath: string;
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  loaders: string;
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  allLoaders: string;
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  query: string;
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  moduleId: string | number;
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  hash: string;
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  namespace: string;
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}
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```
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**Usage Examples:**
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```javascript
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const webpack = require("webpack");
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// Production source maps
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module.exports = {
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  mode: 'production',
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  devtool: false, // Disable default devtool
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  plugins: [
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    new webpack.SourceMapDevToolPlugin({
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      filename: '[file].map[query]',
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      include: /\.(js|css)$/,
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      exclude: /vendor/,
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      moduleFilenameTemplate: 'webpack://[namespace]/[resource-path]?[loaders]',
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      publicPath: 'https://cdn.example.com/sourcemaps/',
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      columns: false,
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      noSources: false
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    })
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  ]
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};
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// Development eval source maps
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module.exports = {
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  mode: 'development',
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  devtool: false,
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  plugins: [
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    new webpack.EvalSourceMapDevToolPlugin({
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      include: /\.js$/,
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      exclude: /node_modules/,
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      moduleFilenameTemplate: 'webpack:///[resource-path]',
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      columns: true
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    })
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  ]
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};
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// Eval debugging without source maps
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module.exports = {
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  mode: 'development',
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  devtool: false,
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  plugins: [
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    new webpack.EvalDevToolModulePlugin({
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      moduleFilenameTemplate: 'webpack:///[resource-path]',
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      sourceUrlComment: '\n//# sourceURL=[url]'
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    })
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  ]
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};
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```
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### Progress Reporting
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The ProgressPlugin provides detailed feedback about compilation progress, helping developers understand build performance and identify bottlenecks.
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```javascript { .api }
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/**
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 * Reports compilation progress during builds with customizable handlers
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 * @param options - Progress reporting configuration
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 */
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class ProgressPlugin {
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  constructor(options?: {
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    /** Show active module count */
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    activeModules?: boolean;
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    /** Show entries progress */
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    entries?: boolean;
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    /** Custom progress handler function */
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    handler?: (percentage: number, message: string, ...args: string[]) => void;
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    /** Show modules progress */
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    modules?: boolean;
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    /** Expected number of modules for percentage calculation */
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    modulesCount?: number;
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    /** Enable performance profiling */
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    profile?: boolean;
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    /** Show dependencies progress */
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    dependencies?: boolean;
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    /** Expected number of dependencies */
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    dependenciesCount?: number;
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    /** Method for calculating percentage */
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    percentBy?: 'entries' | 'modules' | 'dependencies' | null;
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  });
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}
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```
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**Usage Examples:**
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```javascript
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const webpack = require("webpack");
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module.exports = {
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  plugins: [
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    // Basic progress reporting
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    new webpack.ProgressPlugin(),
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    // Custom progress handler
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    new webpack.ProgressPlugin({
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      activeModules: true,
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      entries: true,
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      modules: true,
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      dependencies: true,
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      profile: true,
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      handler: (percentage, message, ...args) => {
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        const percent = Math.round(percentage * 100);
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        const timestamp = new Date().toLocaleTimeString();
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        console.log(`[${timestamp}] ${percent}% ${message} ${args.join(' ')}`);
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      }
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    }),
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    // Integration with build tools
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    new webpack.ProgressPlugin({
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      handler: (percentage, message, ...args) => {
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        if (process.env.CI) {
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          // Minimal output for CI environments
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          if (percentage === 0) console.log('Build started...');
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          if (percentage === 1) console.log('Build completed!');
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        } else {
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          // Rich progress bar for development
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          const width = 50;
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          const filled = Math.round(width * percentage);
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          const bar = '█'.repeat(filled) + '░'.repeat(width - filled);
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          process.stdout.write(`\r[${bar}] ${Math.round(percentage * 100)}% ${message}`);
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          if (percentage === 1) console.log(); // New line when complete
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        }
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      }
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    })
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  ]
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};
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```
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### File Watching System
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Webpack's watching system monitors file changes and triggers rebuilds automatically, essential for development workflows.
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```javascript { .api }
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/**
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 * Manages file watching for automatic rebuilds during development
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 */
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class Watching {
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  /** Associated compiler instance */
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  compiler: Compiler;
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  /** Watch configuration options */
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  options: WatchOptions;
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  /** File system watcher instance */
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  watcher: any;
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  /**
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   * Close watching and cleanup resources
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   * @param callback - Completion callback
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   */
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  close(callback?: () => void): void;
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  /**
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   * Invalidate current compilation and trigger rebuild
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   * @param filename - Optional filename that changed
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   */
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  invalidate(filename?: string): void;
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  /**
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   * Suspend watching temporarily without closing
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   */
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  suspend(): void;
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  /**
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   * Resume watching after suspension
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   */
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  resume(): void;
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}
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/**
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 * Manages multiple watching instances for multi-compiler setups
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 */
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class MultiWatching {
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  /** Array of individual watching instances */
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  watchings: Watching[];
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  /** Multi-compiler instance */
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  compiler: MultiCompiler;
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  /**
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   * Close all watching instances
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   * @param callback - Completion callback
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   */
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  close(callback?: () => void): void;
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  /**
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   * Invalidate all watching instances
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   */
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  invalidate(): void;
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  /**
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   * Suspend all watching instances
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   */
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  suspend(): void;
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  /**
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   * Resume all watching instances
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   */
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  resume(): void;
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}
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/**
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 * Configuration options for file watching behavior
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 */
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interface WatchOptions {
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  /** Delay in milliseconds before rebuilding after change */
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  aggregateTimeout?: number;
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  /** Enable polling for file changes (useful for network drives) */
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  poll?: boolean | number;
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  /** Files, directories, or patterns to ignore */
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  ignored?: string | RegExp | string[] | ((path: string) => boolean);
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  /** Follow symbolic links */
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  followSymlinks?: boolean;
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  /** Use stdin to stop watching in CLI mode */
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  stdin?: boolean;
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}
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/**
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 * Plugin to ignore specific files during watch mode
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 * @param paths - Patterns of files to ignore during watching
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 */
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class WatchIgnorePlugin {
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  constructor(paths: Array<string | RegExp>);
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}
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```
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**Usage Examples:**
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```javascript
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const webpack = require("webpack");
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const path = require("path");
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// Basic watching setup
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const compiler = webpack(config);
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const watching = compiler.watch({
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  aggregateTimeout: 300,
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  poll: 1000,
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  ignored: [
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    path.resolve(__dirname, 'node_modules'),
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    path.resolve(__dirname, 'dist')
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  ]
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}, (err, stats) => {
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  if (err || stats.hasErrors()) {
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    console.error(err || stats.toString());
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    return;
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  }
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  console.log('Rebuild completed!');
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});
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// Advanced watching configuration
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module.exports = {
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  plugins: [
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    new webpack.WatchIgnorePlugin({
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      paths: [
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        /node_modules/,
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        /\.git/,
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        /\.DS_Store/,
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        path.resolve(__dirname, 'temp'),
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        path.resolve(__dirname, 'coverage')
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      ]
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    })
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  ],
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  watchOptions: {
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    aggregateTimeout: 200,
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    poll: false,
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    ignored: [
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      '**/node_modules',
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      '**/.git',
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      '**/temp/**'
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    ],
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    followSymlinks: false
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  }
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};
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// Programmatic watching control
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watching.invalidate(); // Trigger rebuild
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watching.suspend();   // Pause watching
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watching.resume();    // Resume watching
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watching.close(() => {
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  console.log('Watching ended');
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});
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```
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### Development Server Integration
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Integration points and configuration for webpack development servers that provide live reloading, hot module replacement, and development middleware.
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```javascript { .api }
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/**
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 * DevTool options for debugging and development
440
 */
441
type DevTool = 
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  | false
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  | 'eval'
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  | 'eval-cheap-source-map'
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  | 'eval-cheap-module-source-map'
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  | 'eval-source-map'
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  | 'cheap-source-map'
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  | 'cheap-module-source-map'
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  | 'source-map'
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  | 'inline-cheap-source-map'
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  | 'inline-cheap-module-source-map'
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  | 'inline-source-map'
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  | 'eval-nosources-cheap-source-map'
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  | 'eval-nosources-cheap-module-source-map'
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  | 'eval-nosources-source-map'
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  | 'inline-nosources-cheap-source-map'
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  | 'inline-nosources-cheap-module-source-map'
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  | 'inline-nosources-source-map'
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  | 'nosources-cheap-source-map'
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  | 'nosources-cheap-module-source-map'
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  | 'nosources-source-map'
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  | 'hidden-nosources-cheap-source-map'
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  | 'hidden-nosources-cheap-module-source-map'
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  | 'hidden-nosources-source-map'
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  | 'hidden-cheap-source-map'
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  | 'hidden-cheap-module-source-map'
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  | 'hidden-source-map';
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/**
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 * Development mode specific optimizations and settings
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 */
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interface DevelopmentOptions {
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  /** Development tool for debugging */
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  devtool?: DevTool;
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  /** Enable development mode optimizations */
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  mode?: 'development';
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  /** Watch mode configuration */
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  watch?: boolean;
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  /** Watch options */
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  watchOptions?: WatchOptions;
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  /** Development server configuration */
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  devServer?: DevServerOptions;
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  /** Enable caching for development */
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  cache?: boolean | CacheOptions;
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  /** Source map exclude patterns */
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  infrastructureLogging?: {
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    level?: 'none' | 'error' | 'warn' | 'info' | 'log' | 'verbose';
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    debug?: string | RegExp | ((name: string) => boolean);
489
  };
490
}
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492
interface DevServerOptions {
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  /** Enable hot module replacement */
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  hot?: boolean | 'only';
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  /** Enable live reloading */
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  liveReload?: boolean;
497
  /** Development server port */
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  port?: number | string;
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  /** Development server host */
500
  host?: string;
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  /** Enable HTTPS */
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  https?: boolean | ServerOptions;
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  /** Static file serving configuration */
504
  static?: string | StaticOptions | Array<string | StaticOptions>;
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  /** Proxy configuration */
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  proxy?: ProxyConfig;
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  /** History API fallback */
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  historyApiFallback?: boolean | HistoryApiFallbackOptions;
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  /** Overlay for compilation errors */
510
  client?: {
511
    overlay?: boolean | {
512
      errors?: boolean;
513
      warnings?: boolean;
514
    };
515
    progress?: boolean;
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    reconnect?: boolean | number;
517
  };
518
}
519
```
520

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**Usage Examples:**
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523
```javascript
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const webpack = require("webpack");
525

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// Development configuration with optimal debugging
527
module.exports = {
528
  mode: 'development',
529
  devtool: 'eval-source-map',
530
  entry: './src/index.js',
531
  
532
  // Development server setup
533
  devServer: {
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    hot: true,
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    liveReload: true,
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    port: 3000,
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    host: 'localhost',
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    static: {
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      directory: path.join(__dirname, 'public'),
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      publicPath: '/assets'
541
    },
542
    proxy: {
543
      '/api': {
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        target: 'http://localhost:8080',
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        changeOrigin: true,
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        pathRewrite: {
547
          '^/api': ''
548
        }
549
      }
550
    },
551
    historyApiFallback: {
552
      rewrites: [
553
        { from: /^\/$/, to: '/views/landing.html' },
554
        { from: /^\/subpage/, to: '/views/subpage.html' },
555
        { from: /./, to: '/views/404.html' }
556
      ]
557
    },
558
    client: {
559
      overlay: {
560
        errors: true,
561
        warnings: false
562
      },
563
      progress: true
564
    }
565
  },
566
  
567
  // Optimized for development
568
  cache: {
569
    type: 'memory'
570
  },
571
  
572
  infrastructureLogging: {
573
    level: 'info',
574
    debug: ['webpack-dev-server']
575
  },
576
  
577
  plugins: [
578
    new webpack.HotModuleReplacementPlugin(),
579
    new webpack.ProgressPlugin({
580
      activeModules: true,
581
      modules: true,
582
      handler: (percentage, message, ...args) => {
583
        console.log(`${Math.round(percentage * 100)}% ${message} ${args.join(' ')}`);
584
      }
585
    })
586
  ]
587
};
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589
// Multiple development configurations
590
const createDevConfig = (name, port) => ({
591
  name,
592
  mode: 'development',
593
  devtool: 'eval-cheap-module-source-map',
594
  entry: `./src/${name}/index.js`,
595
  devServer: {
596
    port,
597
    hot: true,
598
    allowedHosts: 'all'
599
  },
600
  plugins: [
601
    new webpack.HotModuleReplacementPlugin(),
602
    new webpack.DefinePlugin({
603
      'process.env.SERVICE_NAME': JSON.stringify(name)
604
    })
605
  ]
606
});
607

608
module.exports = [
609
  createDevConfig('frontend', 3000),
610
  createDevConfig('admin', 3001),
611
  createDevConfig('mobile', 3002)
612
];
613
```
614

615
### Error Handling and Reporting
616

617
Comprehensive error handling and reporting capabilities for development debugging and build monitoring.
618

619
```javascript { .api }
620
/**
621
 * Base class for webpack-specific errors with enhanced debugging information
622
 */
623
class WebpackError extends Error {
624
  /** Error name */
625
  name: string;
626
  
627
  /** Error message */
628
  message: string;
629
  
630
  /** Module associated with error */
631
  module?: Module;
632
  
633
  /** Location information */
634
  loc?: SourceLocation;
635
  
636
  /** Error details */
637
  details?: string;
638
  
639
  /** Related file path */
640
  file?: string;
641
  
642
  /** Hide error from stats output */
643
  hideStack?: boolean;
644
  
645
  /** Error chunk */
646
  chunk?: Chunk;
647
  
648
  constructor(message?: string);
649
}
650

651
/**
652
 * Compilation statistics with error and warning information
653
 */
654
class Stats {
655
  /** Associated compilation */
656
  compilation: Compilation;
657
  
658
  /**
659
   * Check if compilation has errors
660
   * @returns True if errors exist
661
   */
662
  hasErrors(): boolean;
663
  
664
  /**
665
   * Check if compilation has warnings
666
   * @returns True if warnings exist
667
   */
668
  hasWarnings(): boolean;
669
  
670
  /**
671
   * Get compilation errors
672
   * @returns Array of error objects
673
   */
674
  toJson(options?: StatsOptions): {
675
    errors: StatsError[];
676
    warnings: StatsError[];
677
    errorDetails?: string;
678
    // ... other stats properties
679
  };
680
}
681

682
interface StatsError {
683
  message: string;
684
  formatted?: string;
685
  moduleId?: string | number;
686
  moduleIdentifier?: string;
687
  moduleName?: string;
688
  loc?: string;
689
  file?: string;
690
  details?: string;
691
}
692

693
interface SourceLocation {
694
  line: number;
695
  column?: number;
696
  index?: number;
697
}
698
```
699

700
**Usage Examples:**
701

702
```javascript
703
const webpack = require("webpack");
704

705
// Enhanced error reporting
706
const compiler = webpack(config);
707

708
compiler.hooks.done.tap('ErrorReporter', (stats) => {
709
  const info = stats.toJson({
710
    all: false,
711
    errors: true,
712
    warnings: true,
713
    errorDetails: true
714
  });
715
  
716
  if (stats.hasErrors()) {
717
    console.error('Build failed with errors:');
718
    info.errors.forEach((error, index) => {
719
      console.error(`\nError ${index + 1}:`);
720
      console.error(`File: ${error.file || 'unknown'}`);
721
      console.error(`Module: ${error.moduleName || 'unknown'}`);
722
      console.error(`Location: ${error.loc || 'unknown'}`);
723
      console.error(`Message: ${error.message}`);
724
      if (error.details) {
725
        console.error(`Details: ${error.details}`);
726
      }
727
    });
728
  }
729
  
730
  if (stats.hasWarnings()) {
731
    console.warn('Build completed with warnings:');
732
    info.warnings.forEach((warning, index) => {
733
      console.warn(`\nWarning ${index + 1}: ${warning.message}`);
734
    });
735
  }
736
});
737

738
// Custom error handling plugin
739
class ErrorHandlerPlugin {
740
  apply(compiler) {
741
    compiler.hooks.compilation.tap('ErrorHandler', (compilation) => {
742
      compilation.hooks.buildModule.tap('ErrorHandler', (module) => {
743
        console.log(`Building module: ${module.identifier()}`);
744
      });
745
      
746
      compilation.hooks.failedModule.tap('ErrorHandler', (module, error) => {
747
        console.error(`Failed to build module: ${module.identifier()}`);
748
        console.error(`Error: ${error.message}`);
749
        
750
        // Enhanced error information
751
        const enhancedError = new WebpackError(
752
          `Module build failed: ${error.message}`
753
        );
754
        enhancedError.module = module;
755
        enhancedError.file = module.resource;
756
        enhancedError.details = error.stack;
757
        
758
        compilation.errors.push(enhancedError);
759
      });
760
    });
761
  }
762
}
763

764
module.exports = {
765
  plugins: [
766
    new ErrorHandlerPlugin()
767
  ],
768
  
769
  stats: {
770
    errors: true,
771
    warnings: true,
772
    errorDetails: true,
773
    colors: true,
774
    modules: false,
775
    chunks: false
776
  }
777
};
778
```
779

780
### Development Mode Optimizations
781

782
Optimizations and settings specifically designed for development builds to improve build speed and debugging experience.
783

784
```javascript { .api }
785
/**
786
 * Development-specific optimization settings
787
 */
788
interface DevelopmentOptimization {
789
  /** Disable minimization in development */
790
  minimize?: false;
791
  
792
  /** Fast module concatenation for development */
793
  concatenateModules?: false;
794
  
795
  /** Remove empty chunks */
796
  removeEmptyChunks?: boolean;
797
  
798
  /** Merge duplicate chunks */
799
  mergeDuplicateChunks?: boolean;
800
  
801
  /** Flag included chunks */
802
  flagIncludedChunks?: false;
803
  
804
  /** Remove available modules optimization */
805
  removeAvailableModules?: false;
806
  
807
  /** Provide bail out reasons for optimizations */
808
  providedExports?: boolean;
809
  
810
  /** Use exports analysis */
811
  usedExports?: boolean;
812
  
813
  /** Enable side effects analysis */
814
  sideEffects?: boolean;
815
  
816
  /** Node environment for process.env.NODE_ENV */
817
  nodeEnv?: 'development';
818
}
819

820
/**
821
 * Cache configuration optimized for development
822
 */
823
interface DevelopmentCache {
824
  /** Cache type */
825
  type: 'memory' | 'filesystem';
826
  
827
  /** Cache name for multiple configurations */
828
  name?: string;
829
  
830
  /** Cache version */
831
  version?: string;
832
  
833
  /** Build dependencies for cache invalidation */
834
  buildDependencies?: {
835
    config?: string[];
836
    defaultWebpack?: string[];
837
  };
838
  
839
  /** Memory cache specific options */
840
  maxGenerations?: number;
841
  cacheUnaffected?: boolean;
842
  
843
  /** Filesystem cache options */
844
  cacheDirectory?: string;
845
  compression?: false | 'gzip' | 'brotli';
846
  hashAlgorithm?: string;
847
  store?: 'pack';
848
  allowCollectingMemory?: boolean;
849
}
850
```
851

852
**Usage Examples:**
853

854
```javascript
855
const webpack = require("webpack");
856
const path = require("path");
857

858
// Optimized development configuration
859
module.exports = {
860
  mode: 'development',
861
  
862
  // Fast rebuilds with memory caching
863
  cache: {
864
    type: 'memory',
865
    maxGenerations: 1,
866
    cacheUnaffected: true
867
  },
868
  
869
  // Development optimizations
870
  optimization: {
871
    minimize: false,
872
    removeAvailableModules: false,
873
    removeEmptyChunks: false,
874
    splitChunks: false,
875
    concatenateModules: false,
876
    flagIncludedChunks: false,
877
    nodeEnv: 'development'
878
  },
879
  
880
  // Fast source maps
881
  devtool: 'eval-cheap-module-source-map',
882
  
883
  // Development-specific plugins
884
  plugins: [
885
    new webpack.HotModuleReplacementPlugin(),
886
    new webpack.NoEmitOnErrorsPlugin(),
887
    
888
    // Enhanced development environment
889
    new webpack.DefinePlugin({
890
      'process.env.NODE_ENV': JSON.stringify('development'),
891
      '__DEV__': true,
892
      '__PROD__': false
893
    }),
894
    
895
    new webpack.ProgressPlugin({
896
      activeModules: false,
897
      entries: true,
898
      handler(percentage, message, ...args) {
899
        // Only show major milestones to reduce noise
900
        if (percentage === 0 || percentage === 1) {
901
          console.log(`${Math.round(percentage * 100)}% ${message}`);
902
        }
903
      }
904
    })
905
  ],
906
  
907
  // Fast resolve for development
908
  resolve: {
909
    symlinks: false,
910
    cacheWithContext: false
911
  },
912
  
913
  // Optimized file watching
914
  watchOptions: {
915
    ignored: [
916
      path.resolve(__dirname, 'node_modules'),
917
      '**/.git',
918
      '**/dist',
919
      '**/build'
920
    ],
921
    aggregateTimeout: 100
922
  },
923
  
924
  // Development-friendly output
925
  output: {
926
    pathinfo: true,
927
    filename: '[name].js',
928
    chunkFilename: '[name].chunk.js'
929
  }
930
};
931

932
// Multi-environment development setup
933
const createDevConfig = (env) => {
934
  const isDevelopment = env === 'development';
935
  const isTest = env === 'test';
936
  
937
  return {
938
    mode: isDevelopment ? 'development' : 'production',
939
    
940
    cache: isDevelopment ? {
941
      type: 'memory',
942
      maxGenerations: 1
943
    } : false,
944
    
945
    devtool: isDevelopment 
946
      ? 'eval-source-map'
947
      : isTest 
948
        ? 'inline-source-map'
949
        : 'source-map',
950
    
951
    plugins: [
952
      ...(isDevelopment ? [
953
        new webpack.HotModuleReplacementPlugin(),
954
        new webpack.ProgressPlugin()
955
      ] : []),
956
      
957
      new webpack.DefinePlugin({
958
        'process.env.NODE_ENV': JSON.stringify(env),
959
        '__DEV__': isDevelopment,
960
        '__TEST__': isTest
961
      })
962
    ],
963
    
964
    optimization: {
965
      minimize: !isDevelopment && !isTest,
966
      removeAvailableModules: !isDevelopment,
967
      concatenateModules: !isDevelopment && !isTest
968
    }
969
  };
970
};
971

972
module.exports = (env, argv) => {
973
  return createDevConfig(env.NODE_ENV || 'development');
974
};
975
```
976

977
## Common Types
978

979
```javascript { .api }
980
interface Compiler {
981
  /** Webpack configuration options */
982
  options: WebpackOptionsNormalized;
983
  
984
  /** Compiler hooks for plugin integration */
985
  hooks: CompilerHooks;
986
  
987
  /** Start watching for file changes */
988
  watch(
989
    watchOptions: WatchOptions,
990
    handler: (err: Error | null, stats?: Stats) => void
991
  ): Watching;
992
  
993
  /** Run single build */
994
  run(callback: (err: Error | null, stats?: Stats) => void): void;
995
  
996
  /** Close compiler and cleanup */
997
  close(callback: (err?: Error) => void): void;
998
}
999

1000
interface Compilation {
1001
  /** Parent compiler */
1002
  compiler: Compiler;
1003
  
1004
  /** Compilation errors */
1005
  errors: WebpackError[];
1006
  
1007
  /** Compilation warnings */
1008
  warnings: WebpackError[];
1009
  
1010
  /** Generated assets */
1011
  assets: Record<string, Asset>;
1012
  
1013
  /** Get logger for compilation */
1014
  getLogger(name: string): WebpackLogger;
1015
}
1016

1017
interface WebpackLogger {
1018
  /** Log error message */
1019
  error(...args: any[]): void;
1020
  
1021
  /** Log warning message */
1022
  warn(...args: any[]): void;
1023
  
1024
  /** Log info message */
1025
  info(...args: any[]): void;
1026
  
1027
  /** Log debug message */
1028
  log(...args: any[]): void;
1029
  
1030
  /** Log debug message */
1031
  debug(...args: any[]): void;
1032
  
1033
  /** Log trace message */
1034
  trace(...args: any[]): void;
1035
  
1036
  /** Get child logger */
1037
  getChildLogger(name: string): WebpackLogger;
1038
}
1039

1040
type WebpackPluginInstance = {
1041
  apply(compiler: Compiler): void;
1042
};
1043

1044
interface CacheOptions {
1045
  type: 'memory' | 'filesystem';
1046
  name?: string;
1047
  version?: string;
1048
  cacheDirectory?: string;
1049
  buildDependencies?: {
1050
    config?: string[];
1051
    defaultWebpack?: string[];
1052
  };
1053
}
1054
```
1055

1056
## Development Workflow Patterns
1057

1058
### Hot Module Replacement Workflow
1059

1060
```javascript
1061
// webpack.config.js
1062
module.exports = {
1063
  entry: './src/index.js',
1064
  mode: 'development',
1065
  devServer: {
1066
    hot: true,
1067
    port: 3000
1068
  },
1069
  plugins: [
1070
    new webpack.HotModuleReplacementPlugin()
1071
  ]
1072
};
1073

1074
// src/index.js - HMR setup
1075
import { render } from './app';
1076

1077
render();
1078

1079
if (module.hot) {
1080
  module.hot.accept('./app', () => {
1081
    const { render } = require('./app');
1082
    render();
1083
  });
1084
}
1085
```
1086

1087
### Development Server with Proxy
1088

1089
```javascript
1090
module.exports = {
1091
  devServer: {
1092
    hot: true,
1093
    proxy: {
1094
      '/api': 'http://localhost:8080',
1095
      '/ws': {
1096
        target: 'ws://localhost:8080',
1097
        ws: true
1098
      }
1099
    },
1100
    historyApiFallback: true,
1101
    client: {
1102
      overlay: {
1103
        errors: true,
1104
        warnings: false
1105
      }
1106
    }
1107
  }
1108
};
1109
```
1110

1111
### Multi-Configuration Development
1112

1113
```javascript
1114
module.exports = [
1115
  // Client configuration
1116
  {
1117
    name: 'client',
1118
    target: 'web',
1119
    entry: './src/client/index.js',
1120
    plugins: [
1121
      new webpack.HotModuleReplacementPlugin()
1122
    ]
1123
  },
1124
  // Server configuration
1125
  {
1126
    name: 'server',
1127
    target: 'node',
1128
    entry: './src/server/index.js',
1129
    plugins: [
1130
      new webpack.WatchIgnorePlugin({
1131
        paths: [/\.js$/, /\.d\.ts$/]
1132
      })
1133
    ]
1134
  }
1135
];
1136
```
1137

1138
The development tools ecosystem in webpack provides everything needed for efficient development workflows, from basic file watching to advanced hot module replacement and comprehensive debugging capabilities.