很多人会纳闷为什么网上的webpack配置less的内容中的webpack.config.dev.js和自己的webpack.config.dev.js展示出来的不一样，那是因为webpack版本不一致造成的，之前过早的帖子只是针对于老版本的webpack配置，不适合新版本，下面我将分别给大家给出高低版本的webpack配置less的方案

如果用create-react-app创建出react项目，那么如下图所示，所有安装的的东西会放在scripts中

09_57_29__12_11_2018.jpg

其中"scripts"帮你自动下载需要的 webpack-dev-server 依赖,包括开始start，打包build，测试test，配置都放在eject中，所以如果想要配置自带的依赖外的less的东西需要暴露出eject依赖文件

yarn add less-loader或者npm install less-loader//先安装依赖
yarn eject 或者npm run eject//解构目录

执行上面操作之后，自动会生成config文件夹，需要修改webpack.config.dev.js和webpack.config.prod.js两个文件，打开config目录下的webpack.config.dev.js，修改webpack配置，如下图

10_16_03__12_11_2018.jpg

高版本webpack配置less

在配置文件中做了两处修改

第一处是找到 cssRegex和cssModuleRegex 在他们得我下面新建lessRegex和lessModuleRegex变量

第二处是增加 less-loader的配置

具体修改如下

//第一块大概在38行左右
const lessRegex = /\.less$/;
const lessModuleRegex = /\.module\.less$/;
//第二块大概在318行左右
 //配置less
{
 test: lessRegex,
 exclude: lessModuleRegex,
 use: getStyleLoaders({ importLoaders: 2 }, 'less-loader'),
},
{
  test: lessModuleRegex,
  use: getStyleLoaders(
{
  importLoaders: 2,
  modules: true,
  getLocalIdent: getCSSModuleLocalIdent,
   },
 'less-loader'
 ),
 },

完整代码如下

'use strict';

const fs = require('fs');
const path = require('path');
const resolve = require('resolve');
const webpack = require('webpack');
const PnpWebpackPlugin = require('pnp-webpack-plugin');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const CaseSensitivePathsPlugin = require('case-sensitive-paths-webpack-plugin');
const InterpolateHtmlPlugin = require('react-dev-utils/InterpolateHtmlPlugin');
const WatchMissingNodeModulesPlugin = require('react-dev-utils/WatchMissingNodeModulesPlugin');
const ModuleScopePlugin = require('react-dev-utils/ModuleScopePlugin');
const getCSSModuleLocalIdent = require('react-dev-utils/getCSSModuleLocalIdent');
const getClientEnvironment = require('./env');
const paths = require('./paths');
const ManifestPlugin = require('webpack-manifest-plugin');
const ModuleNotFoundPlugin = require('react-dev-utils/ModuleNotFoundPlugin');
const ForkTsCheckerWebpackPlugin = require('fork-ts-checker-webpack-plugin-alt');
const typescriptFormatter = require('react-dev-utils/typescriptFormatter');


// Webpack uses `publicPath` to determine where the app is being served from.
// In development, we always serve from the root. This makes config easier.
const publicPath = '/';
// `publicUrl` is just like `publicPath`, but we will provide it to our app
// as %PUBLIC_URL% in `index.html` and `process.env.PUBLIC_URL` in JavaScript.
// Omit trailing slash as %PUBLIC_PATH%/xyz looks better than %PUBLIC_PATH%xyz.
const publicUrl = '';
// Get environment variables to inject into our app.
const env = getClientEnvironment(publicUrl);

// Check if TypeScript is setup
const useTypeScript = fs.existsSync(paths.appTsConfig);

// style files regexes
const cssRegex = /\.css$/;
const cssModuleRegex = /\.module\.css$/;
const lessRegex = /\.less$/;
const lessModuleRegex = /\.module\.less$/;
const sassRegex = /\.(scss|sass)$/;
const sassModuleRegex = /\.module\.(scss|sass)$/;

// common function to get style loaders
const getStyleLoaders = (cssOptions, preProcessor) => {
  const loaders = [
    require.resolve('style-loader'),
    {
      loader: require.resolve('css-loader'),
      options: cssOptions,
    },
    {
      // Options for PostCSS as we reference these options twice
      // Adds vendor prefixing based on your specified browser support in
      // package.json
      loader: require.resolve('postcss-loader'),
      options: {
        // Necessary for external CSS imports to work
        // https://github.com/facebook/create-react-app/issues/2677
        ident: 'postcss',
        plugins: () => [
          require('postcss-flexbugs-fixes'),
          require('postcss-preset-env')({
            autoprefixer: {
              flexbox: 'no-2009',
            },
            stage: 3,
          }),
        ],
      },
    },
  ];
  if (preProcessor) {
    loaders.push(require.resolve(preProcessor));
  }
  return loaders;
};

// This is the development configuration.
// It is focused on developer experience and fast rebuilds.
// The production configuration is different and lives in a separate file.
module.exports = {
  mode: 'development',
  // You may want 'eval' instead if you prefer to see the compiled output in DevTools.
  // See the discussion in https://github.com/facebook/create-react-app/issues/343
  devtool: 'cheap-module-source-map',
  // These are the "entry points" to our application.
  // This means they will be the "root" imports that are included in JS bundle.
  entry: [
    // Include an alternative client for WebpackDevServer. A client's job is to
    // connect to WebpackDevServer by a socket and get notified about changes.
    // When you save a file, the client will either apply hot updates (in case
    // of CSS changes), or refresh the page (in case of JS changes). When you
    // make a syntax error, this client will display a syntax error overlay.
    // Note: instead of the default WebpackDevServer client, we use a custom one
    // to bring better experience for Create React App users. You can replace
    // the line below with these two lines if you prefer the stock client:
    // require.resolve('webpack-dev-server/client') + '?/',
    // require.resolve('webpack/hot/dev-server'),
    require.resolve('react-dev-utils/webpackHotDevClient'),
    // Finally, this is your app's code:
    paths.appIndexJs,
    // We include the app code last so that if there is a runtime error during
    // initialization, it doesn't blow up the WebpackDevServer client, and
    // changing JS code would still trigger a refresh.
  ],
  output: {
    // Add /* filename */ comments to generated require()s in the output.
    pathinfo: true,
    // This does not produce a real file. It's just the virtual path that is
    // served by WebpackDevServer in development. This is the JS bundle
    // containing code from all our entry points, and the Webpack runtime.
    filename: 'static/js/bundle.js',
    // There are also additional JS chunk files if you use code splitting.
    chunkFilename: 'static/js/[name].chunk.js',
    // This is the URL that app is served from. We use "/" in development.
    publicPath: publicPath,
    // Point sourcemap entries to original disk location (format as URL on Windows)
    devtoolModuleFilenameTemplate: info =>
      path.resolve(info.absoluteResourcePath).replace(/\\/g, '/'),
  },
  optimization: {
    // Automatically split vendor and commons
    // https://twitter.com/wSokra/status/969633336732905474
    // https://medium.com/webpack/webpack-4-code-splitting-chunk-graph-and-the-splitchunks-optimization-be739a861366
    splitChunks: {
      chunks: 'all',
      name: false,
    },
    // Keep the runtime chunk seperated to enable long term caching
    // https://twitter.com/wSokra/status/969679223278505985
    runtimeChunk: true,
  },
  resolve: {
    // This allows you to set a fallback for where Webpack should look for modules.
    // We placed these paths second because we want `node_modules` to "win"
    // if there are any conflicts. This matches Node resolution mechanism.
    // https://github.com/facebook/create-react-app/issues/253
    modules: ['node_modules'].concat(
      // It is guaranteed to exist because we tweak it in `env.js`
      process.env.NODE_PATH.split(path.delimiter).filter(Boolean)
    ),
    // These are the reasonable defaults supported by the Node ecosystem.
    // We also include JSX as a common component filename extension to support
    // some tools, although we do not recommend using it, see:
    // https://github.com/facebook/create-react-app/issues/290
    // `web` extension prefixes have been added for better support
    // for React Native Web.
    extensions: paths.moduleFileExtensions
      .map(ext => `.${ext}`)
      .filter(ext => useTypeScript || !ext.includes('ts')),
    alias: {
      // Support React Native Web
      // https://www.smashingmagazine.com/2016/08/a-glimpse-into-the-future-with-react-native-for-web/
      'react-native': 'react-native-web',
    },
    plugins: [
      // Adds support for installing with Plug'n'Play, leading to faster installs and adding
      // guards against forgotten dependencies and such.
      PnpWebpackPlugin,
      // Prevents users from importing files from outside of src/ (or node_modules/).
      // This often causes confusion because we only process files within src/ with babel.
      // To fix this, we prevent you from importing files out of src/ -- if you'd like to,
      // please link the files into your node_modules/ and let module-resolution kick in.
      // Make sure your source files are compiled, as they will not be processed in any way.
      new ModuleScopePlugin(paths.appSrc, [paths.appPackageJson]),
    ],
  },
  resolveLoader: {
    plugins: [
      // Also related to Plug'n'Play, but this time it tells Webpack to load its loaders
      // from the current package.
      PnpWebpackPlugin.moduleLoader(module),
    ],
  },
  module: {
    strictExportPresence: true,
    rules: [
      // Disable require.ensure as it's not a standard language feature.
      { parser: { requireEnsure: false } },

      // First, run the linter.
      // It's important to do this before Babel processes the JS.
      {
        test: /\.(js|mjs|jsx)$/,
        enforce: 'pre',
        use: [
          {
            options: {
              formatter: require.resolve('react-dev-utils/eslintFormatter'),
              eslintPath: require.resolve('eslint'),
              
            },
            loader: require.resolve('eslint-loader'),
          },
        ],
        include: paths.appSrc,
      },
      {
        // "oneOf" will traverse all following loaders until one will
        // match the requirements. When no loader matches it will fall
        // back to the "file" loader at the end of the loader list.
        oneOf: [
          // "url" loader works like "file" loader except that it embeds assets
          // smaller than specified limit in bytes as data URLs to avoid requests.
          // A missing `test` is equivalent to a match.
          {
            test: [/\.bmp$/, /\.gif$/, /\.jpe?g$/, /\.png$/],
            loader: require.resolve('url-loader'),
            options: {
              limit: 10000,
              name: 'static/media/[name].[hash:8].[ext]',
            },
          },
          // Process application JS with Babel.
          // The preset includes JSX, Flow, and some ESnext features.
          {
            test: /\.(js|mjs|jsx|ts|tsx)$/,
            include: paths.appSrc,
            loader: require.resolve('babel-loader'),
            options: {
              customize: require.resolve(
                'babel-preset-react-app/webpack-overrides'
              ),
              
              plugins: [
                [
                  require.resolve('babel-plugin-named-asset-import'),
                  {
                    loaderMap: {
                      svg: {
                        ReactComponent: '@svgr/webpack?-prettier,-svgo![path]',
                      },
                    },
                  },
                ],
              ],
              // This is a feature of `babel-loader` for webpack (not Babel itself).
              // It enables caching results in ./node_modules/.cache/babel-loader/
              // directory for faster rebuilds.
              cacheDirectory: true,
              // Don't waste time on Gzipping the cache
              cacheCompression: false,
            },
          },
          // Process any JS outside of the app with Babel.
          // Unlike the application JS, we only compile the standard ES features.
          {
            test: /\.(js|mjs)$/,
            exclude: /@babel(?:\/|\\{1,2})runtime/,
            loader: require.resolve('babel-loader'),
            options: {
              babelrc: false,
              configFile: false,
              compact: false,
              presets: [
                [
                  require.resolve('babel-preset-react-app/dependencies'),
                  { helpers: true },
                ],
              ],
              cacheDirectory: true,
              // Don't waste time on Gzipping the cache
              cacheCompression: false,
              
              // If an error happens in a package, it's possible to be
              // because it was compiled. Thus, we don't want the browser
              // debugger to show the original code. Instead, the code
              // being evaluated would be much more helpful.
              sourceMaps: false,
            },
          },
          // "postcss" loader applies autoprefixer to our CSS.
          // "css" loader resolves paths in CSS and adds assets as dependencies.
          // "style" loader turns CSS into JS modules that inject <style> tags.
          // In production, we use a plugin to extract that CSS to a file, but
          // in development "style" loader enables hot editing of CSS.
          // By default we support CSS Modules with the extension .module.css
          {
            test: cssRegex,
            exclude: cssModuleRegex,
            use: getStyleLoaders({
              importLoaders: 1,
            }),
          },
          // Adds support for CSS Modules (https://github.com/css-modules/css-modules)
          // using the extension .module.css
          {
            test: cssModuleRegex,
            use: getStyleLoaders({
              importLoaders: 1,
              modules: true,
              getLocalIdent: getCSSModuleLocalIdent,
            }),
          },
          // Opt-in support for SASS (using .scss or .sass extensions).
          // Chains the sass-loader with the css-loader and the style-loader
          // to immediately apply all styles to the DOM.
          // By default we support SASS Modules with the
          // extensions .module.scss or .module.sass
          {
            test: sassRegex,
            exclude: sassModuleRegex,
            use: getStyleLoaders({ importLoaders: 2 }, 'sass-loader'),
          },
          // Adds support for CSS Modules, but using SASS
          // using the extension .module.scss or .module.sass
          {
            test: sassModuleRegex,
            use: getStyleLoaders(
              {
                importLoaders: 2,
                modules: true,
                getLocalIdent: getCSSModuleLocalIdent,
              },
              'sass-loader'
            ),
          },
          //配置less
          {
            test: lessRegex,
            exclude: lessModuleRegex,
            use: getStyleLoaders({ importLoaders: 2 }, 'less-loader'),
          },
          {
            test: lessModuleRegex,
            use: getStyleLoaders(
              {
                importLoaders: 2,
                modules: true,
                getLocalIdent: getCSSModuleLocalIdent,
              },
              'less-loader'
            ),
          },

          // "file" loader makes sure those assets get served by WebpackDevServer.
          // When you `import` an asset, you get its (virtual) filename.
          // In production, they would get copied to the `build` folder.
          // This loader doesn't use a "test" so it will catch all modules
          // that fall through the other loaders.
          {
            // Exclude `js` files to keep "css" loader working as it injects
            // its runtime that would otherwise be processed through "file" loader.
            // Also exclude `html` and `json` extensions so they get processed
            // by webpacks internal loaders.
            exclude: [/\.(js|mjs|jsx|ts|tsx)$/, /\.html$/, /\.json$/],
            loader: require.resolve('file-loader'),
            options: {
              name: 'static/media/[name].[hash:8].[ext]',
            },
          },
        ],
      },
      // ** STOP ** Are you adding a new loader?
      // Make sure to add the new loader(s) before the "file" loader.
    ],
  },
  plugins: [
    // Generates an `index.html` file with the <script> injected.
    new HtmlWebpackPlugin({
      inject: true,
      template: paths.appHtml,
    }),
    // Makes some environment variables available in index.html.
    // The public URL is available as %PUBLIC_URL% in index.html, e.g.:
    // <link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
    // In development, this will be an empty string.
    new InterpolateHtmlPlugin(HtmlWebpackPlugin, env.raw),
    // This gives some necessary context to module not found errors, such as
    // the requesting resource.
    new ModuleNotFoundPlugin(paths.appPath),
    // Makes some environment variables available to the JS code, for example:
    // if (process.env.NODE_ENV === 'development') { ... }. See `./env.js`.
    new webpack.DefinePlugin(env.stringified),
    // This is necessary to emit hot updates (currently CSS only):
    new webpack.HotModuleReplacementPlugin(),
    // Watcher doesn't work well if you mistype casing in a path so we use
    // a plugin that prints an error when you attempt to do this.
    // See https://github.com/facebook/create-react-app/issues/240
    new CaseSensitivePathsPlugin(),
    // If you require a missing module and then `npm install` it, you still have
    // to restart the development server for Webpack to discover it. This plugin
    // makes the discovery automatic so you don't have to restart.
    // See https://github.com/facebook/create-react-app/issues/186
    new WatchMissingNodeModulesPlugin(paths.appNodeModules),
    // Moment.js is an extremely popular library that bundles large locale files
    // by default due to how Webpack interprets its code. This is a practical
    // solution that requires the user to opt into importing specific locales.
    // https://github.com/jmblog/how-to-optimize-momentjs-with-webpack
    // You can remove this if you don't use Moment.js:
    new webpack.IgnorePlugin(/^\.\/locale$/, /moment$/),
    // Generate a manifest file which contains a mapping of all asset filenames
    // to their corresponding output file so that tools can pick it up without
    // having to parse `index.html`.
    new ManifestPlugin({
      fileName: 'asset-manifest.json',
      publicPath: publicPath,
    }),
    // TypeScript type checking
    useTypeScript &&
      new ForkTsCheckerWebpackPlugin({
        typescript: resolve.sync('typescript', {
          basedir: paths.appNodeModules,
        }),
        async: false,
        checkSyntacticErrors: true,
        tsconfig: paths.appTsConfig,
        compilerOptions: {
          module: 'esnext',
          moduleResolution: 'node',
          resolveJsonModule: true,
          isolatedModules: true,
          noEmit: true,
          jsx: 'preserve',
        },
        reportFiles: [
          '**',
          '!**/*.json',
          '!**/__tests__/**',
          '!**/?(*.)(spec|test).*',
          '!src/setupProxy.js',
          '!src/setupTests.*',
        ],
        watch: paths.appSrc,
        silent: true,
        formatter: typescriptFormatter,
      }),
  ].filter(Boolean),

  // Some libraries import Node modules but don't use them in the browser.
  // Tell Webpack to provide empty mocks for them so importing them works.
  node: {
    dgram: 'empty',
    fs: 'empty',
    net: 'empty',
    tls: 'empty',
    child_process: 'empty',
  },
  // Turn off performance processing because we utilize
  // our own hints via the FileSizeReporter
  performance: false,
};

同样webpack.config.prod.js开发环境中也做一样的修改

切记万万不可将整个文件复制过去，毕竟安装的东西都不一样，按需复制即可

低版本webpack配置less

在配置文件中做了三处修改

  // 第一处是找到 `test: /\.css$/` 将其改为  `test: /\.(css|less)$/`
  // 第二处是增加 `less-loader`的配置
  // 第三处是在exclude属性中增加 `/\.(css|less)$/` 
  // 具体修改如下
  module: {
    ...
    {
      // test: /\.css$/  第一处 
      test: /\.(css|less)$/,
      use: [
        require.resolve('style-loader'),
        ...
        // 第二处
        {
          loader: require.resolve('less-loader')
        }
      ]
    },
    {
      exclude: [
        /\.(js|jsx|mjs)$/, 
        /\.html$/, 
        /\.json$/,
        // 第三处
        /\.(css|less)$/,
      ]
    }
  }

PS:本人只是一枚废柴小码农，在实战中积累经验，只是将所踩过的坑分享出来给遇到同样坑的小伙伴们提个醒，可能会少走些弯路。如果能帮助到你解决实际问题，我将更加坚定分享的初衷：一起成长。
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