详解vue-cli脚手架中webpack配置方法

config
├── dev.env.js /https://img.qb5200.com/download-x/dev环境变量配置
├── index.js // dev和prod环境的一些基本配置
└── prod.env.js // prod环境变量配置
build
├── build.js // npm run build所执行的脚本
├── check-versions.js // 检查npm和node的版本
├── logo.png
├── utils.js // 一些工具方法，主要用于生成cssLoader和styleLoader配置
├── vue-loader.conf.js // vueloader的配置信息
├── webpack.base.conf.js // dev和prod的公共配置
├── webpack.dev.conf.js // dev环境的配置
└── webpack.prod.conf.js // prod环境的配置

use strict //[采用严格模式]
/**
* [webpack-merge提供了一个合并函数，它将数组和合并对象创建一个新对象
] 
*/
const merge = require('webpack-merge')
const prodEnv = require('./prod.env')

module.exports = merge(prodEnv, {
 NODE_ENV: '"development"'
})

use strict
module.exports = {
NODE_ENV: '"production"'
}

const path = require('path')
module.exports = {
 /**
  * [开发环境配置]
  */
dev: {
  assetsSubDirectory: 'static', // [子目录,一般存放css,js,image等文件]
assetsPublicPath: '/', // [根目录]
/**
* [配置服务代理] 
*/
  proxyTable: {
   '/hcm': {
    target: 'https://127.0.0.1:8448',
    changeOrigin: true,
    secure: false
   },
   headers: {
    "Access-Control-Allow-Origin": "*",
    "Access-Control-Allow-Methods": "GET, POST, PUT, DELETE, PATCH, OPTIONS",
    "Access-Control-Allow-Headers": "X-Requested-With, content-type, Authorization"
   }
  },
  host: '127.0.0.1', // [浏览器访问地址]
  port: 8083, // [端口号设置，端口号占用出现问题可在此处修改]
  autoOpenBrowser: true, // [是否在编译（输入命令行npm run dev）后打开http://127.0.0.1:8083/页面]
  errorOverlay: true, // [浏览器错误提示]
  notifyOnErrors: true, // [跨平台错误提示]
  poll:false, // [使用文件系统(file system)获取文件改动的通知devServer.watchOptions] 
  useEslint: true, // [是否启用代码规范检查]
  showEslintErrorsInOverlay: false, // [是否展示eslint的错误提示]
  devtool: 'eval-source-map', // [增加调试，该属性为原始源代码]
  cacheBusting: true, // [使缓存失效]
  cssSourceMap: false // [代码压缩后进行调bug定位将非常困难，于是引入sourcemap记录压缩前后的位置信息记录，当产生错误时直接定位到未压缩前的位置，将大大的方便我们调试]
 },
/**
* [生产环境配置] 
*/
 build: {
 /**
* [index、login、license、forbidden、notfound、Internal.licenses编译后生成的位置和名字，根据需要改变后缀] 
*/
  index: path.resolve(__dirname, '../../hcm-modules/hcm-web/src/main/resources/META-INF/resources/index.html'),
  login: path.resolve(__dirname, '../../hcm-modules/hcm-web/src/main/resources/META-INF/resources/login.html'),
  license: path.resolve(__dirname, '../../hcm-modules/hcm-web/src/main/resources/META-INF/resources/license.html'),
  forbidden: path.resolve(__dirname, '../../hcm-modules/hcm-web/src/main/resources/META-INF/resources/error/403.html'),
  notfound: path.resolve(__dirname, '../../hcm-modules/hcm-web/src/main/resources/META-INF/resources/error/404.html'),
  internal: path.resolve(__dirname, '../../hcm-modules/hcm-web/src/main/resources/META-INF/resources/error/500.html'),
  licenses: path.resolve(__dirname, '../../hcm-modules/hcm-web/src/main/resources/META-INF/resourceshttps://img.qb5200.com/download-x/docs/licenses.html'),
/**
* [编译后存放生成环境代码的位置] 
*/
  assetsRoot: path.resolve(__dirname, '../../hcm-modules/hcm-web/src/main/resources/META-INF/resources'),
  assetsSubDirectory: 'static', //js、css、images存放文件夹名
  assetsPublicPath: './', //发布的根目录，通常本地打包dist后打开文件会报错，此处修改为./。如果是上线的文件，可根据文件存放位置进行更改路径
  productionSourceMap: true,
  devtool: '#source-map',
  productionGzip: false, //unit的gzip命令用来压缩文件，gzip模式下需要压缩的文件的扩展名有js和css
  productionGzipExtensions: ['js', 'css'],
  bundleAnalyzerReport: process.env.npm_config_report //打包分析
 }
}

require('./check-versions')() //check-versions：调用检查版本的文件。加（）代表直接调用该函数
process.env.NODE_ENV = 'production' //设置当前是生产环境
/**
*下面定义常量引入插件
*/
const ora = require('ora') //加载动画
const rm = require('rimraf') //删除文件
const path = require('path')
const chalk = require('chalk') //对文案输出的一个彩色设置
const webpack = require('webpack')
const config = require('../config') //默认读取下面的index.js文件
const webpackConfig = require('./webpack.prod.conf')
const spinner = ora('building for production...') //调用start的方法实现加载动画，优化用户体验
spinner.start()
//先删除dist文件再生成新文件，因为有时候会使用hash来命名，删除整个文件可避免冗余
rm(path.join(config.build.assetsRoot, config.build.assetsSubDirectory), err => {
 if (err) throw err
 webpack(webpackConfig, (err, stats) => {
  spinner.stop()
  if (err) throw err
  process.stdout.write(stats.toString({
   colors: true,
   modules: false,
   children: false,
   chunks: false,
   chunkModules: false
  }) + '\n\n')
  if (stats.hasErrors()) {
   console.log(chalk.red(' Build failed with errors.\n'))
   process.exit(1)
  }
  console.log(chalk.cyan(' Build complete.\n'))
  console.log(chalk.yellow(
   ' Tip: built files are meant to be served over an HTTP server.\n' +
   ' Opening index.html over file:// won\'t work.\n'
  ))
 })
})

const chalk = require('chalk') 
const semver = require('semver') //对版本进行检查
const packageConfig = require('../package.json')
const shell = require('shelljs')
function exec (cmd) {
 //返回通过child_process模块的新建子进程，执行 Unix 系统命令后转成没有空格的字符串
 return require('child_process').execSync(cmd).toString().trim()
}
const versionRequirements = [
 {
  name: 'node',
  currentVersion: semver.clean(process.version), //使用semver格式化版本
  versionRequirement: packageConfig.engines.node //获取package.json中设置的node版本
 }
]
if (shell.which('npm')) {
 versionRequirements.push({
  name: 'npm',
  currentVersion: exec('npm --version'), // 自动调用npm --version命令，并且把参数返回给exec函数，从而获取纯净的版本号
  versionRequirement: packageConfig.engines.npm
 })
}
module.exports = function () {
 const warnings = []
 for (let i = 0; i < versionRequirements.length; i++) {
  const mod = versionRequirements[i]
  if (!semver.satisfies(mod.currentVersion, mod.versionRequirement)) {
   //上面这个判断就是如果版本号不符合package.json文件中指定的版本号，就执行下面错误提示的代码
warnings.push(mod.name + ': ' +
    chalk.red(mod.currentVersion) + ' should be ' +
    chalk.green(mod.versionRequirement)
   )
  }
 }
 if (warnings.length) {
  console.log('')
  console.log(chalk.yellow('To use this template, you must update following to modules:'))
  console.log()
  for (let i = 0; i < warnings.length; i++) {
   const warning = warnings[i]
   console.log(' ' + warning)
  }
  console.log()
  process.exit(1)
 }
}

const path = require('path')
const config = require('../config')
const ExtractTextPlugin = require('extract-text-webpack-plugin')
const packageConfig = require('../package.json')
exports.assetsPath = function (_path) {
 const assetsSubDirectory = process.env.NODE_ENV === 'production'
  ? config.build.assetsSubDirectory
  : config.dev.assetsSubDirectory
 return path.posix.join(assetsSubDirectory, _path)
}
exports.cssLoaders = function (options) {
 options = options || {}
//使用了css-loader和postcssLoader，通过options.usePostCSS属性来判断是否使用postcssLoader中压缩等方法

 const cssLoader = {
  loader: 'css-loader',
  options: {
   sourceMap: options.sourceMap
  }
 }
 const postcssLoader = {
  loader: 'postcss-loader',
  options: {
   sourceMap: options.sourceMap
  }
 }
 // generate loader string to be used with extract text plugin
 function generateLoaders (loader, loaderOptions) {
  const loaders = options.usePostCSS ? [cssLoader, postcssLoader] : [cssLoader]
  if (loader) {
   loaders.push({
    loader: loader + '-loader',
  //Object.assign是es6语法的浅复制，后两者合并后复制完成赋值
    options: Object.assign({}, loaderOptions, {
     sourceMap: options.sourceMap
    })
   })
  }
  // Extract CSS when that option is specified
  // (which is the case during production build)
if (options.extract) {
//ExtractTextPlugin可提取出文本，代表首先使用上面处理的loaders，当未能正确引入时使用vue-style-loader
   return ExtractTextPlugin.extract({
    use: loaders,
    fallback: 'vue-style-loader',
    publicPath: '../../'
   })
} else {
//返回vue-style-loader连接loaders的最终值
   return ['vue-style-loader'].concat(loaders)
  }
 }
 // https://vue-loader.vuejs.org/en/configurations/extract-css.html
 return {
  css: generateLoaders(),//需要css-loader 和 vue-style-loader
  postcss: generateLoaders(),//需要css-loader和postcssLoader 和 vue-style-loader
  less: generateLoaders('less'), //需要less-loader 和 vue-style-loader
  sass: generateLoaders('sass', { indentedSyntax: true }), //需要sass-loader 和 vue-style-loader
  scss: generateLoaders('sass'), //需要sass-loader 和 vue-style-loader
  stylus: generateLoaders('stylus'), //需要stylus-loader 和 vue-style-loader
  styl: generateLoaders('stylus') //需要stylus-loader 和 vue-style-loader
 }
}
// Generate loaders for standalone style files (outside of .vue)
exports.styleLoaders = function (options) {
 const output = []
 const loaders = exports.cssLoaders(options)
//将各种css,less,sass等综合在一起得出结果输出output
 for (const extension in loaders) {
  const loader = loaders[extension]
  output.push({
   test: new RegExp('\\.' + extension + '$'),
   use: loader
  })
 }
 return output
}
exports.createNotifierCallback = () => {
//发送跨平台通知系统
 const notifier = require('node-notifier')
 return (severity, errors) => {
if (severity !== 'error') return
//当报错时输出错误信息的标题，错误信息详情，副标题以及图标
  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')
  })
 }
}

const utils = require('./utils')
const config = require('../config')
const isProduction = process.env.NODE_ENV === 'production'
const sourceMapEnabled = isProduction
 ? config.build.productionSourceMap
 : config.dev.cssSourceMap
//处理项目中的css文件，生产环境和测试环境默认是打开sourceMap，而extract中的提取样式到单独文件只有在生产环境中才需要
module.exports = {
 loaders: utils.cssLoaders({
  sourceMap: sourceMapEnabled,
  extract: isProduction
 }),
 cssSourceMap: sourceMapEnabled,
 cacheBusting: config.dev.cacheBusting,
// 在模版编译过程中，编译器可以将某些属性，如 src 路径，转换为require调用，以便目标资源可以由 webpack 处理
 transformToRequire: {
  video: ['src', 'poster'],
  source: 'src',
  img: 'src',
  image: 'xlink:href'
 }
}

const path = require('path')
const utils = require('./utils')
/**
* [引入index.js文件路径] 
*/
const config = require('../config')
const vueLoaderConfig = require('./vue-loader.conf')

/**
 * [获取文件路径]
 * @param dir [文件名称]
 *_dirname为当前模块文件所在目录的绝对路径* 
 *@return 文件绝对路径
*/
function resolve (dir) {
 return path.join(__dirname, '..', dir)
}
const createLintingRule = () => ({
 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, '../'),
  /**
    * [入口文件配置]
   */
 entry: {
/**
    * [入口文件路径, babel-polyfill是对es6语法的支持]
   */
  app: ['babel-polyfill', './src/main.js'],
  login: ['babel-polyfill', './src/loginMain.js'],
  license: ['babel-polyfill', './src/licenseMain.js']
 },
/**
  * [文件导出配置]
*/
 output: {
  path: config.build.assetsRoot,
  filename: '[name].js',
  publicPath: process.env.NODE_ENV === 'production'
   ? config.build.assetsPublicPath
   : config.dev.assetsPublicPath //公共存放路径
 },
 resolve: {
  /**
    * [extensions: 配置文件的扩展名,当在important文件时,不用需要添加扩展名]
   */
extensions: ['.js', '.vue', '.json'],
/**
    * [alias 给路径定义别名]
*/
  alias: {
   'vue$': 'vuehttps://img.qb5200.com/download-x/dist/vue.esm.js',
   '@': resolve('src')
  }
 },
/**
*使用插件配置相应文件的处理方法
*/
 module: {
rules: [
   ...(config.dev.useEslint ? [createLintingRule()] : []),
/**
   * [使用vue-loader将vue文件转化成js的模块]
*/
   {
    test: /\.vue$/,
    loader: 'vue-loader',
    options: vueLoaderConfig
   },
/**
    * [通过babel-loader将js进行编译成es5/es6 文件]
*/
   {
    test: /\.js$/,
    loader: 'babel-loader',
    include: [resolve('src'), resolve('test')]
   },
/**
   * [图片、音像、字体都使用url-loader进行处理，超过10000会编译成base64]
*/
   {
    test: /\.(png|jpe?g|gif|svg)(\?.*)?$/,
    loader: 'url-loader',
    options: {
     limit: 10000,
     name: utils.assetsPath('img/[name].[hash:7].[ext]')
    }
   },
   {
    test: /\.(mp4|webm|ogg|mp3|wav|flac|aac)(\?.*)?$/,
    loader: 'url-loader',
    options: {
     limit: 10000,
     name: utils.assetsPath('media/[name].[hash:7].[ext]')
    }
   },
   {
    test: /\.(woff2?|eot|ttf|otf)(\?.*)?$/,
    loader: 'url-loader',
    options: {
     limit: 10000,
     name: utils.assetsPath('fonts/[name].[hash:7].[ext]')
    }
   },
/**
    * [canvas 解析]
*/
   {
    test: path.resolve(`${resolve('src')}/lib/jtopo.js`),
    loader: ['exports-loader?window.JTopo', 'script-loader']
   }
  ]
 },
//以下选项是Node.js全局变量或模块，这里主要是防止webpack注入一些Node.js的东西到vue中 
 node: {
  setImmediate: false,
  dgram: 'empty',
  fs: 'empty',
  net: 'empty',                           
  tls: 'empty',
  child_process: 'empty'
 }
}

const path = require('path')
const utils = require('./utils')
const webpack = require('webpack')
const config = require('../config')
//通过webpack-merge实现webpack.dev.conf.js对wepack.base.config.js的继承
const merge = require('webpack-merge')
const baseWebpackConfig = require('./webpack.base.conf')
const HtmlWebpackPlugin = require('html-webpack-plugin')
//美化webpack的错误信息和日志的插件
const FriendlyErrorsPlugin = require('friendly-errors-webpack-plugin')
// 查看空闲端口位置，默认情况下搜索8000这个端口
const portfinder = require('portfinder')
// processs为node的一个全局对象获取当前程序的环境变量，即host
const HOST = process.env.HOST
const PORT = process.env.PORT && Number(process.env.PORT)
function resolveApp(relativePath) {
 return path.resolve(relativePath);
}
const devWebpackConfig = merge(baseWebpackConfig, {
 module: {
//规则是工具utils中处理出来的styleLoaders，生成了css，less,postcss等规则
  rules: utils.styleLoaders({ sourceMap: config.dev.cssSourceMap, usePostCSS: true })
 },
// 增强调试
 devtool: config.dev.devtool,
// 此处的配置都是在config的index.js中设定好了
 devServer: {
//控制台显示的选项有none, error, warning 或者 info
clientLogLevel: 'warning',
//使用 HTML5 History API
historyApiFallback: true,
hot: true, //热加载
compress: true, //压缩
  host: HOST || config.dev.host,
port: PORT || config.dev.port,
open: config.dev.autoOpenBrowser, //调试时自动打开浏览器
  overlay: config.dev.errorOverlay
   ? { warnings: false, errors: true }
   : false,
  publicPath: config.dev.assetsPublicPath,
proxy: config.dev.proxyTable,//接口代理
quiet: true, //控制台是否禁止打印警告和错误,若用FriendlyErrorsPlugin 此处为 true  watchOptions: {
   poll: config.dev.poll, // 文件系统检测改动
  }
 },
 plugins: [
  new webpack.DefinePlugin({
   'process.env': require('../confighttps://img.qb5200.com/download-x/dev.env')
  }),
new webpack.HotModuleReplacementPlugin(),//模块热替换插件，修改模块时不需要刷新页面
new webpack.NamedModulesPlugin(), // 显示文件的正确名字
new webpack.NoEmitOnErrorsPlugin(), //当webpack编译错误的时候，来中端打包进程，防止错误代码打包到文件中
// https://github.com/ampedandwired/html-webpack-plugin
// 该插件可自动生成一个 html5 文件或使用模板文件将编译好的代码注入进去 
new HtmlWebpackPlugin({
   filename: 'index.html',
   template: 'index.html',
   inject: true,
   chunks: ['app']
  }),
  new HtmlWebpackPlugin({
   filename: 'login.html',
   template: 'login.html',
   inject: true,
   chunks: ['login']
  }),
  new HtmlWebpackPlugin({
   filename: 'license.html',
   template: 'license.html',
   inject: true,
   chunks: ['license']
  }),
  new HtmlWebpackPlugin({
   filename: 'licenses.html',
   template: 'licenses.html',
   inject: true,
   chunks: []
  }),
  new HtmlWebpackPlugin({
   filename: '404.html',
   template: path.resolve(__dirname, '../errors/404.html'),
   favicon: resolveApp('favicon.ico'),
   inject: true,
   chunks: []
  }),
  new HtmlWebpackPlugin({
   filename: '403.html',
   template: path.resolve(__dirname, '../errors/403.html'),
   favicon: resolveApp('favicon.ico'),
   inject: true,
   chunks: []
  }),
  new HtmlWebpackPlugin({
   filename: '500.html',
   template: path.resolve(__dirname, '../errors/500.html'),
   favicon: resolveApp('favicon.ico'),
   inject: true,
   chunks: []
  })
 ]
})

module.exports = new Promise((resolve, reject) => {
 portfinder.basePort = process.env.PORT || config.dev.port
//查找端口号
 portfinder.getPort((err, port) => {
  if (err) {
   reject(err)
} else {
//端口被占用时就重新设置evn和devServer的端口
   process.env.PORT = port
   // add port to devServer config
   devWebpackConfig.devServer.port = port
//友好地输出信息
   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)
  }
 })
})

const path = require('path')
const utils = require('./utils')
const webpack = require('webpack')
const config = require('../config')
const merge = require('webpack-merge')
const baseWebpackConfig = require('./webpack.base.conf')
const CopyWebpackPlugin = require('copy-webpack-plugin')
const HtmlWebpackPlugin = require('html-webpack-plugin')
const ExtractTextPlugin = require('extract-text-webpack-plugin')
const OptimizeCSSPlugin = require('optimize-css-assets-webpack-plugin')
const UglifyJsPlugin = require('uglifyjs-webpack-plugin')

const env = require('../config/prod.env')
function resolveApp(relativePath) {
 return path.resolve(relativePath);
}
const webpackConfig = merge(baseWebpackConfig, {
 module: {
  rules: utils.styleLoaders({
   sourceMap: config.build.productionSourceMap,//开启调试的模式。默认为true
   extract: true,
   usePostCSS: true
  })
 },
 devtool: config.build.productionSourceMap ? config.build.devtool : false,
 output: {
  path: config.build.assetsRoot,
  filename: utils.assetsPath('js/[name].[chunkhash].js'),
  chunkFilename: utils.assetsPath('js/[id].[chunkhash].js')
 },
 plugins: [
  // http://vuejs.github.io/vue-loader/en/workflow/production.html
  new webpack.DefinePlugin({
   'process.env': env
  }),
  new UglifyJsPlugin({
   uglifyOptions: {
    compress: {
     warnings: false //警告：true保留警告，false不保留
    }
   },
   sourceMap: config.build.productionSourceMap,
   parallel: true
  }),
// extract css into its own file
//抽取文本。比如打包之后的index页面有style插入，就是这个插件抽取出来的，减少请求
new ExtractTextPlugin({
   filename: utils.assetsPath('css/[name].[contenthash].css'),
   allChunks: true,
}),
//优化css的插件
  new OptimizeCSSPlugin({
   cssProcessorOptions: config.build.productionSourceMap
    ? { safe: true, map: { inline: false } }
    : { safe: true }
  }),
  //html打包
  new HtmlWebpackPlugin({
   filename: config.build.index,
   template: 'index.html',
   inject: true,
//压缩
   minify: {
    removeComments: true, //删除注释
    collapseWhitespace: true, //删除空格
    removeAttributeQuotes: true //删除属性的引号
   },
   chunks: ['vendor', 'manifest', 'app'],
   // necessary to consistently work with multiple chunks via CommonsChunkPlugin
   chunksSortMode: 'dependency'
  }),
  new HtmlWebpackPlugin({
   filename: config.build.login,
   template: 'login.html',
   inject: true,
   minify: {
    removeComments: true,
    collapseWhitespace: true,
    removeAttributeQuotes: true
   },
   chunks: ['vendor', 'manifest', 'login'],
   // necessary to consistently work with multiple chunks via CommonsChunkPlugin
   chunksSortMode: 'dependency'
  }),
  new HtmlWebpackPlugin({
   filename: config.build.license,
   template: 'license.html',
   inject: true,
   minify: {
    removeComments: true,
    collapseWhitespace: true,
    removeAttributeQuotes: true
   },
   chunks: ['vendor', 'manifest', 'license'],
   // necessary to consistently work with multiple chunks via CommonsChunkPlugin
   chunksSortMode: 'dependency'
  }),
  new HtmlWebpackPlugin({
   filename: config.build.notfound,
   template: path.resolve(__dirname, '../errors/404.html'),
   inject: true,
   favicon: resolveApp('favicon.ico'),
   minify: {
    removeComments: true,
    collapseWhitespace: true,
    removeAttributeQuotes: true
   },
   chunks: [],
   // necessary to consistently work with multiple chunks via CommonsChunkPlugin
   chunksSortMode: 'dependency'
  }),
  new HtmlWebpackPlugin({
   filename: config.build.forbidden,
   template: path.resolve(__dirname, '../errors/403.html'),
   inject: true,
   favicon: resolveApp('favicon.ico'),
   minify: {
    removeComments: true,
    collapseWhitespace: true,
    removeAttributeQuotes: true
   },
   chunks: [],
   // necessary to consistently work with multiple chunks via CommonsChunkPlugin
   chunksSortMode: 'dependency'
  }),
  new HtmlWebpackPlugin({
   filename: config.build.internal,
   template: path.resolve(__dirname, '../errors/500.html'),
   inject: true,
   favicon: resolveApp('favicon.ico'),
   minify: {
    removeComments: true,
    collapseWhitespace: true,
    removeAttributeQuotes: true
   },
   chunks: [],
   // necessary to consistently work with multiple chunks via CommonsChunkPlugin
   chunksSortMode: 'dependency'
  }),
  new HtmlWebpackPlugin({
   filename: config.build.licenses,
   template: 'licenses.html',
   inject: true,
   minify: {
    removeComments: true,
    collapseWhitespace: true,
    removeAttributeQuotes: true
   },
   chunks: [],
   // necessary to consistently work with multiple chunks via CommonsChunkPlugin
   chunksSortMode: 'dependency'
  }),
  // keep module.id stable when vender modules does not change
  new webpack.HashedModuleIdsPlugin(),
  // enable scope hoisting
new webpack.optimize.ModuleConcatenationPlugin(),
//抽取公共的模块, 提升你的代码在浏览器中的执行速度。
  new webpack.optimize.CommonsChunkPlugin({
   name: 'vendor',
   minChunks (module) {
    // 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({
   name: 'manifest',
   minChunks: Infinity
}),
// 预编译所有模块到一个闭包中， 
 new webpack.optimize.CommonsChunkPlugin({
   name: 'app',
   async: 'vendor-async',
   children: true,
   minChunks: 3
  }),
//复制，比如打包完之后需要把打包的文件复制到dist里面
  new CopyWebpackPlugin([
   {
    from: path.resolve(__dirname, '../static'),
    to: config.build.assetsSubDirectory,
    ignore: ['.*']
   }
  ])
 ]
})

if (config.build.productionGzip) {
 const 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
  })
 )
}
// 提供带 Content-Encoding 编码的压缩版的资源
if (config.build.bundleAnalyzerReport) {
 const BundleAnalyzerPlugin = require('webpack-bundle-analyzer').BundleAnalyzerPlugin
 webpackConfig.plugins.push(new BundleAnalyzerPlugin())
}
module.exports = webpackConfig