一分钟让你学会webpack中各个文件的作用

- 日理万妓 2022-12-13 04:24 292阅读 0赞

导语：  
我们在使用webpack的过程中，总是会看到项目里很多文件，但是对于新手来说，可能不知道它们对应的作用，秉持着能用就行，不需要看懂，够用就行。这种相信是大部分人都是这种想法，包括以前的我，这种想法是错的。

**想要进阶，就必须会修改webpack的配置，要想会修改，就必须懂这些文件，代码的作用。**

### webpack文件和代码功能介绍 ###

*  一，built目录
 *   *  1，util.js
     *  2，webpack.base.conf.js
     *  3，webpack.dev.conf.js
     *  4，webpack.prod.config.js
 *  二，config目录
 *   *  1，dev.env.js
     *  2，prod.env.js
     *  3，index.js

# 一，built目录 #

## 1，util.js ##

'use strict'
    const path = require('path')
    const config = require('../config')
    const ExtractTextPlugin = require('extract-text-webpack-plugin')
    const packageConfig = require('../package.json')
    
    // 返回资源文件存放的路径
    exports.assetsPath = function (_path) { 
    	//判断当前是开发模式还是生产模式
      const assetsSubDirectory = process.env.NODE_ENV === 'production'
        ? config.build.assetsSubDirectory
        : config.dev.assetsSubDirectory
    
      return path.posix.join(assetsSubDirectory, _path)
    }
    
    //生成cssLoaders，用于加载.vue文件中的样式。
    exports.cssLoaders = function (options) { 
      options = options || { }
    
      const cssLoader = { 
        loader: 'css-loader',
        options: { 
          sourceMap: options.sourceMap
        }
      }
    
      const postcssLoader = { 
        loader: 'postcss-loader',
        options: { 
          sourceMap: options.sourceMap
        }
      }
    
      // 生成要与提取文本插件一起使用的加载程序字符串
      function generateLoaders (loader, loaderOptions) { 
        const loaders = options.usePostCSS ? [cssLoader, postcssLoader] : [cssLoader]
    
        if (loader) { 
          loaders.push({ 
            loader: loader + '-loader',
            options: Object.assign({ }, loaderOptions, { 
              sourceMap: options.sourceMap
            })
          })
        }
    
        // Extract CSS when that option is specified
        // (which is the case during production build)
        if (options.extract) { 
          return ExtractTextPlugin.extract({ 
            use: loaders,
            fallback: 'vue-style-loader'
          })
        } else { 
          return ['vue-style-loader'].concat(loaders)
        }
      }
    
      // https://vue-loader.vuejs.org/en/configurations/extract-css.html
      return { 
        css: generateLoaders(),
        postcss: generateLoaders(),
        less: generateLoaders('less'),
        sass: generateLoaders('sass', {  indentedSyntax: true }),
        scss: generateLoaders('sass'),
        stylus: generateLoaders('stylus'),
        styl: generateLoaders('stylus')
      }
    }
    
    // 生成styleloaders用于加载不在.vue文件中的css样式
    exports.styleLoaders = function (options) { 
      const output = []
      const loaders = exports.cssLoaders(options)
    
      for (const extension in loaders) { 
        const loader = loaders[extension]
        output.push({ 
          test: new RegExp('\\.' + extension + '$'),
          use: loader
        })
      }
    
      return output
    }
    /** * 结束添加 * @returns {Function} */
    exports.createNotifierCallback = () => { 
      const notifier = require('node-notifier')
    
      return (severity, errors) => { 
        if (severity !== 'error') return
    
        const error = errors[0]
        const filename = error.file && error.file.split('!').pop()
    
        notifier.notify({ 
          title: packageConfig.name,
          message: severity + ': ' + error.name,
          subtitle: filename || '',
          icon: path.join(__dirname, 'logo.png')
        })
      }
    }

## 2，webpack.base.conf.js ##

'use strict'
    const path = require('path')
    const utils = require('./utils')
    const config = require('../config')
    const vueLoaderConfig = require('./vue-loader.conf')
    
    /** * 获取绝对路径 * @param dir * @returns {*|string} */
    function resolve (dir) { 
      return path.join(__dirname, '..', dir)
    }
    
    //eslint的配置
    const createLintingRule = () => ({ 
    //对.js和.vue结尾的文件进行eslint
      test: /\.(js|vue)$/,
      loader: 'eslint-loader',
      enforce: 'pre',
      include: [resolve('src'), resolve('test')],
      options: { 
        formatter: require('eslint-friendly-formatter'),
        emitWarning: !config.dev.showEslintErrorsInOverlay
      }
    })
    
    module.exports = { 
      context: path.resolve(__dirname, '../'),
      /** * webpack入口文件 */
      // 修改开始
      entry: utils.entries(),
      // 修改结束
    
      // webpack输出路径和命名规则
      output: { 
        path: config.build.assetsRoot,
        filename: '[name].js',
        publicPath: process.env.NODE_ENV === 'production'
          ? config.build.assetsPublicPath
          : config.dev.assetsPublicPath
      },
      // 模块resolve的规则
      resolve: { 
        // 取别名，方便引用模块，例如有了别名之后
        // import Vue from 'vue/dist/vue.common.js'可以写成 import Vue from 'vue
        extensions: ['.js', '.vue', '.json'],
        alias: { 
          'vue$': 'vue/dist/vue.esm.js',
          '@': resolve('src'),
          // 也可以自己添加一些经常引用的路径
          '~': resolve('static')
        }
      },
      // 不同类型模块的处理规则
      module: { 
        rules: [
          ...(config.dev.useEslint ? [createLintingRule()] : []),
          {  // 对所有.vue文件使用vue-loader进行编译
            test: /\.vue$/,
            loader: 'vue-loader',
            options: vueLoaderConfig
          },
          { // 对所有.js文件使用babel-loader进行编译
            test: /\.js$/,
            loader: 'babel-loader',
            include: [resolve('src'), resolve('test'), resolve('node_modules/webpack-dev-server/client')]
          },
          {  // 对图片资源文件使用url-loader
            test: /\.(png|jpe?g|gif|svg)(\?.*)?$/,
            loader: 'url-loader',
            options: { 
              limit: 10000, // 小于10k 的图片转成base64编码的dataURL字符串写到代码中
              name: utils.assetsPath('img/[name].[hash:7].[ext]')// 其他的图片转移到静态资源文件夹
            }
          },
          {  // 对多媒体文件使用url-loader
            test: /\.(mp4|webm|ogg|mp3|wav|flac|aac)(\?.*)?$/,
            loader: 'url-loader',
            options: { 
              limit: 10000,
              name: utils.assetsPath('media/[name].[hash:7].[ext]')
            }
          },
          {  // 对字体资源文件使用url-loader
            test: /\.(woff2?|eot|ttf|otf)(\?.*)?$/,
            loader: 'url-loader',
            options: { 
              limit: 10000,
              name: utils.assetsPath('fonts/[name].[hash:7].[ext]')
            }
          }
        ]
      },
      node: { 
        // 防止Webpack因为Vue而注入无用的setImmediate polyfill
        // source contains it (although only uses it if it's native).
        setImmediate: false,
        // prevent webpack from injecting mocks to Node native modules
        // that does not make sense for the client
        dgram: 'empty',
        fs: 'empty',
        net: 'empty',
        tls: 'empty',
        child_process: 'empty'
      }
    }

## 3，webpack.dev.conf.js ##

'use strict'
    const utils = require('./utils')
    const webpack = require('webpack')
    const config = require('../config')
    const merge = require('webpack-merge')
    const path = require('path')
    const baseWebpackConfig = require('./webpack.base.conf')
    const CopyWebpackPlugin = require('copy-webpack-plugin')
    const HtmlWebpackPlugin = require('html-webpack-plugin')
    const FriendlyErrorsPlugin = require('friendly-errors-webpack-plugin')
    const portfinder = require('portfinder')
    //host和端口
    const HOST = process.env.HOST
    const PORT = process.env.PORT && Number(process.env.PORT)
    //dev状态下webpack的一些配置
    const devWebpackConfig = merge(baseWebpackConfig, { 
      module: { 
      //规则设置是否开启 css 的 sourse map功能，开启了就能很容易定位到某个元素的css的位置
        rules: utils.styleLoaders({  sourceMap: config.dev.cssSourceMap, usePostCSS: true })
      },
      // cheap-module-eval-source-map is faster for development
      //使用cheap-module-eval-source-map作为调试工具
      devtool: config.dev.devtool,
    
      // these devServer options should be customized in /config/index.js
      devServer: { 
      //开发状态下的日志等级
        clientLogLevel: 'warning',
        historyApiFallback: { 
          rewrites: [
          //设置默认主界面
            {  from: /.*/, to: path.posix.join(config.dev.assetsPublicPath, 'index.html') },
          ],
        },
        hot: true,	//热重载
        contentBase: false, // since we use CopyWebpackPlugin.
        compress: true,	//当他为true的时候，它会对所有服务器资源采用gzip进行压缩。
        host: HOST || config.dev.host,
        port: PORT || config.dev.port,
        open: config.dev.autoOpenBrowser,	//在DevServer第一次构建完成时，自动用浏览器打开网页，默认是true
        //该属性是用来在编译出错的时候，在浏览器页面上显示错误
        overlay: config.dev.errorOverlay	
          ? {  warnings: false, errors: true }
          : false,
        publicPath: config.dev.assetsPublicPath,	//配置项用于打开指定 URL 的网页。
        proxy: config.dev.proxyTable,	//有一个单独的API后端开发服务器，并且想要在同一个域上发送API请求时，则代理这些 url
        quiet: true, // 终端只有启动信息，没有其他的
        //监听文件是否有被修改过
        watchOptions: { 
          poll: config.dev.poll,
        }
      },
      plugins: [
        new webpack.DefinePlugin({ 
          'process.env': require('../config/dev.env')
        }),
        new webpack.HotModuleReplacementPlugin(),//热重载
        new webpack.NamedModulesPlugin(), // HMR shows correct file names in console on update.
        new webpack.NoEmitOnErrorsPlugin(),	//跳过编译时出错的代码使编译后的代码不会发生错误
        // 根据你提供的html模板生成html
        new HtmlWebpackPlugin({ 
          filename: 'index.html',
          template: 'index.html',
          inject: true
        }),
        // copy custom static assets
        new CopyWebpackPlugin([
          { 
            from: path.resolve(__dirname, '../static'),
            to: config.dev.assetsSubDirectory,
            ignore: ['.*']
          }
        ])
      ]
    })
    
    module.exports = new Promise((resolve, reject) => { 
      portfinder.basePort = process.env.PORT || config.dev.port
      portfinder.getPort((err, port) => { 
        if (err) { 
          reject(err)
        } else { 
          // publish the new Port, necessary for e2e tests
          process.env.PORT = port
          // add port to devServer config
          devWebpackConfig.devServer.port = port
    
          // 添加 FriendlyErrorsPlugin
          devWebpackConfig.plugins.push(new FriendlyErrorsPlugin({ 
            compilationSuccessInfo: { 
              messages: [`Your application is running here: http://${ devWebpackConfig.devServer.host}:${ port}`],
            },
            onErrors: config.dev.notifyOnErrors
            ? utils.createNotifierCallback()
            : undefined
          }))
    
          resolve(devWebpackConfig)
        }
      })
    })

## 4，webpack.prod.config.js ##

var path = require('path')
    var config = require('../config')
    var utils = require('./utils')
    var webpack = require('webpack')
    var merge = require('webpack-merge')// 一个可以合并数组和对象的插件
    var baseWebpackConfig = require('./webpack.base.conf')
    // 用于从webpack生成的bundle中提取文本到特定文件中的插件
    // 可以抽取出css，js文件将其与webpack输出的bundle分离
    var ExtractTextPlugin = require('extract-text-webpack-plugin')  //如果我们想用webpack打包成一个文件，css js分离开，需要这个插件
    var HtmlWebpackPlugin = require('html-webpack-plugin')// 一个用于生成HTML文件并自动注入依赖文件（link/script）的webpack插件
    var env = config.build.env
    // 合并基础的webpack配置
    var webpackConfig = merge(baseWebpackConfig, { 
        // 配置样式文件的处理规则，使用styleLoaders
      module: { 
        loaders: utils.styleLoaders({  sourceMap: config.build.productionSourceMap, extract: true })
      },
      devtool: config.build.productionSourceMap ? '#source-map' : false, // 开启source-map，生产环境下推荐使用cheap-source-map或source-map，后者得到的.map文件体积比较大，但是能够完全还原以前的js代码
      output: { 
        path: config.build.assetsRoot,// 编译输出目录
        filename: utils.assetsPath('js/[name].[chunkhash].js'),  // 编译输出文件名格式
        chunkFilename: utils.assetsPath('js/[id].[chunkhash].js')  // 没有指定输出名的文件输出的文件名格式
      },
      vue: {  // vue里的css也要单独提取出来
        loaders: utils.cssLoaders({  // css加载器，调用了utils文件中的cssLoaders方法,用来返回针对各类型的样式文件的处理方式,
          sourceMap: config.build.productionSourceMap,
          extract: true
        })
      },
      // 重新配置插件项
      plugins: [
        // http://vuejs.github.io/vue-loader/en/workflow/production.html
        // 位于开发环境下
        new webpack.DefinePlugin({ 
          'process.env': env
        }),
        new webpack.optimize.UglifyJsPlugin({ // 丑化压缩代码
          compress: { 
            warnings: false
          }
        }),
        new webpack.optimize.OccurenceOrderPlugin(),
        // extract css into its own file
        new ExtractTextPlugin(utils.assetsPath('css/[name].[contenthash].css')),  // 抽离css文件
        // generate dist index.html with correct asset hash for caching.
        // you can customize output by editing /index.html
        // see https://github.com/ampedandwired/html-webpack-plugin
         // filename 生成网页的HTML名字，可以使用/来控制文件文件的目录结构，最
          // 终生成的路径是基于webpac配置的output.path的
        new HtmlWebpackPlugin({ 
            // 生成html文件的名字，路径和生产环境下的不同，要与修改后的publickPath相结合，否则开启服务器后页面空白
          filename: config.build.index,
          // 源文件，路径相对于本文件所在的位置
          template: 'index.html',
          inject: true,// 要把<script>标签插入到页面哪个标签里(body|true|head|false)
          minify: { 
            removeComments: true,
            collapseWhitespace: true,
            removeAttributeQuotes: true
            // more options:
            // https://github.com/kangax/html-minifier#options-quick-reference
          },
          // necessary to consistently work with multiple chunks via CommonsChunkPlugin
          chunksSortMode: 'dependency'
        }),
        // 如果文件是多入口的文件，可能存在，重复代码，把公共代码提取出来，又不会重复下载公共代码了
        // （多个页面间会共享此文件的缓存）
        // CommonsChunkPlugin的初始化常用参数有解析？
        // name: 这个给公共代码的chunk唯一的标识
        // filename，如何命名打包后生产的js文件，也是可以用上[name]、[hash]、[chunkhash]
        // minChunks，公共代码的判断标准：某个js模块被多少个chunk加载了才算是公共代码
        // split vendor js into its own file
        new webpack.optimize.CommonsChunkPlugin({ 
          name: 'vendor',
          minChunks: function (module, count) { 
            // any required modules inside node_modules are extracted to vendor
            return (
              module.resource &&
              /\.js$/.test(module.resource) &&
              module.resource.indexOf(
                path.join(__dirname, '../node_modules')
              ) === 0
            )
          }
        }),
        // extract webpack runtime and module manifest to its own file in order to
        // prevent vendor hash from being updated whenever app bundle is updated
        new webpack.optimize.CommonsChunkPlugin({  // 为组件分配ID，通过这个插件webpack可以分析和优先考虑使用最多的模块，并为它们分配最小的ID
          name: 'manifest',
          chunks: ['vendor']
        })
      ]
    })
    // gzip模式下需要引入compression插件进行压缩
    if (config.build.productionGzip) { 
      var CompressionWebpackPlugin = require('compression-webpack-plugin')
     
      webpackConfig.plugins.push(
        new CompressionWebpackPlugin({ 
          asset: '[path].gz[query]',
          algorithm: 'gzip',
          test: new RegExp(
            '\\.(' +
            config.build.productionGzipExtensions.join('|') +
            ')$'
          ),
          threshold: 10240,
          minRatio: 0.8
        })
      )
    }
    if (config.build.bundleAnalyzerReport) { 
    	 const BundleAnalyzerPlugin = require('webpack-bundle-analyzer').BundleAnalyzerPlugin
    	 webpackConfig.plugins.push(new BundleAnalyzerPlugin())
    }
    module.exports = webpackConfig

# 二，config目录 #

## 1，dev.env.js ##

开发模式下的配置

## 2，prod.env.js ##

生产模式下的配置

## 3，index.js ##

共同的配置

'use strict'
    // Template version: 1.3.1
    // see http://vuejs-templates.github.io/webpack for documentation.
    
    const path = require('path')
    
    module.exports = { 
      dev: { 
    
        // Paths
        assetsSubDirectory: 'static',
        assetsPublicPath: '/',
        proxyTable: { },
    
        // Various Dev Server settings
        host: 'localhost', // can be overwritten by process.env.HOST
        port: 8080, // can be overwritten by process.env.PORT, if port is in use, a free one will be determined
        autoOpenBrowser: false,
        errorOverlay: true,
        notifyOnErrors: true,
        poll: false, // https://webpack.js.org/configuration/dev-server/#devserver-watchoptions-
    
        // Use Eslint Loader?
        // If true, your code will be linted during bundling and
        // linting errors and warnings will be shown in the console.
        useEslint: true,
        // If true, eslint errors and warnings will also be shown in the error overlay
        // in the browser.
        showEslintErrorsInOverlay: false,
    
        /** * Source Maps */
    
        // https://webpack.js.org/configuration/devtool/#development
        devtool: 'cheap-module-eval-source-map',
    
        // If you have problems debugging vue-files in devtools,
        // set this to false - it *may* help
        // https://vue-loader.vuejs.org/en/options.html#cachebusting
        cacheBusting: true,
    
        cssSourceMap: true
      },
    
      build: { 
        // Template for index.html
        index: path.resolve(__dirname, '../dist/index.html'),
    
        // Paths
        assetsRoot: path.resolve(__dirname, '../dist'),
        assetsSubDirectory: 'static',
        assetsPublicPath: '/',
    
        /** * Source Maps */
    
        productionSourceMap: true,
        // https://webpack.js.org/configuration/devtool/#production
        devtool: '#source-map',
    
        // Gzip off by default as many popular static hosts such as
        // Surge or Netlify already gzip all static assets for you.
        // Before setting to `true`, make sure to:
        // npm install --save-dev compression-webpack-plugin
        productionGzip: false,
        productionGzipExtensions: ['js', 'css'],
    
        // Run the build command with an extra argument to
        // View the bundle analyzer report after build finishes:
        // `npm run build --report`
        // Set to `true` or `false` to always turn it on or off
        bundleAnalyzerReport: process.env.npm_config_report
      }
    }

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