解析

webpack.base.conf.js

配有一些基础要素包括，会和 通常的webapck.config.js类似。

// 0. 引入一些依赖
var path = require('path')
var utils = require('./utils')
var config = require('../config')
var vueLoaderConfig = require('./vue-loader.conf')

function resolve (dir) {
  return path.join(__dirname, '..', dir)
}

module.exports = {
  entry: {                  // 1. 入口文件配置
    app: './src/main.js'
  },
  output: {                 // 2. 输出文件配置
    path: config.build.assetsRoot,    // 输出目录的绝对路径
    filename: '[name].js',            // 输出的文件的名称，name为对应entry的key
    publicPath: process.env.NODE_ENV === 'production'   // 生产模式或开发模式下html、js等文件内部引用的公共路径(请求的静态资源绝对路径)
      ? config.build.assetsPublicPath  
      : config.dev.assetsPublicPath
  },                        
  resolve: {                // 3. 文件解析配置，设置模块如何被解析
    // 在代码中通过require/import模块的相关配置，预定义了.js 和.vue的扩展，这样在引用一个hello.js文件时，我们只需要import Hello from '/path/to/directory/hello'就能够做到
    extensions: ['.js', '.vue', '.json'],   // 自动解析确定的拓展名,使导入模块时不带拓展名，即在require/import模块路径中自动补全文件后缀
    alias: {                                // 路径的别名，require/import模块路径中可以通过别名缩短路径字符串的长度，节省了大量时间去计算文件与文件之间的嵌套关系
      'vue$': 'vue/dist/vue.esm.js',
      '@': resolve('src'),
    }
  },
  module: {                 // 4. 模块解析配置，如何处理项目不同类型的模块
    rules: [
      {
        test: /\.(js|vue)$/,      // 代码文件后缀
        loader: 'eslint-loader',
        enforce: "pre",
        include: [resolve('src'), resolve('test')],
        options: {
          formatter: require('eslint-friendly-formatter')
        }
      },
      {
        test: /\.vue$/,           // vue文件后缀
        loader: 'vue-loader',
        options: vueLoaderConfig
      },
      {
        test: /\.js$/,            // js文件后缀
        loader: 'babel-loader',
        include: [resolve('src'), resolve('test')]
      },
      {
        test: /\.(png|jpe?g|gif|svg)(\?.*)?$/,        // 图片文件后缀
        loader: 'url-loader',
        query: {
          limit: 10000, // 当图片大小小于10kb时，会生成一个base64串打包到编译后的js文件里，若超过10kb会单独生成一个文件
          name: utils.assetsPath('img/[name].[hash:7].[ext]')
        }
      },
      {
        test: /\.(woff2?|eot|ttf|otf)(\?.*)?$/,       // 字体文件后缀
        loader: 'url-loader',
        query: {
          limit: 10000,
          name: utils.assetsPath('fonts/[name].[hash:7].[ext]')
        }
      }
    ]
  }
}

webpack.dev.conf.js

这个配置将针对我们本机开发时使用。

var utils = require('./utils')          // 工具方法
var webpack = require('webpack')
var config = require('../config')
var merge = require('webpack-merge')    // 合并配置文件
var baseWebpackConfig = require('./webpack.base.conf') // 开发时和运行时共享的的webpack配置文件
var HtmlWebpackPlugin = require('html-webpack-plugin') // 操作html文件的插件
var FriendlyErrorsPlugin = require('friendly-errors-webpack-plugin')

Object.keys(baseWebpackConfig.entry).forEach(function (name) {    // 启用热加载       
  baseWebpackConfig.entry[name] = ['./build/dev-client'].concat(baseWebpackConfig.entry[name])
})

module.exports = merge(baseWebpackConfig, {
  module: {   //通过传入一些配置来获取rules配置，此处传入了sourceMap: false,表示不生成sourceMap
    rules: utils.styleLoaders({ sourceMap: config.dev.cssSourceMap })
  },
  devtool: '#cheap-module-eval-source-map',         // 指定sourceMap类型 方便源码定位
  plugins: [                                        // 一些额外的插件，不是必须的
    new webpack.DefinePlugin({                  // 编译时配置的全局变量
      'process.env': config.dev.env   //当前环境为开发环境
    }),
    new webpack.HotModuleReplacementPlugin(),   // 热更新插件
    new webpack.NoEmitOnErrorsPlugin(),         // 不触发错误,即编译后运行的包正常运行，编译出错时跳过那部分代码
    new HtmlWebpackPlugin({                     // 以现有html为模板去生成新的html以及相应配置，比如编译后文件的引入
      filename: 'index.html', //生成的文件名
      template: 'index.html', //模板
      inject: true            // 表示css、js路径自动添加到该html文件里（css->header标签,js->body），也可配置
    }),
    new FriendlyErrorsPlugin()                  // 友好的错误提示
  ]
})

webpack.prod.conf.js

生产环境下的webpack配置，通过merge方法合并webpack.base.conf.js基础配置，这个文件将定义打包好的生成文件。

var path = require('path')
var utils = require('./utils')
var webpack = require('webpack')
var config = require('../config')
var merge = require('webpack-merge')
var baseWebpackConfig = require('./webpack.base.conf')
var CopyWebpackPlugin = require('copy-webpack-plugin')
var HtmlWebpackPlugin = require('html-webpack-plugin')
var ExtractTextPlugin = require('extract-text-webpack-plugin')          // 针对 vue文件里的样式单独拆分，这样他们会被合并到css文件里去
var OptimizeCSSPlugin = require('optimize-css-assets-webpack-plugin')

var env = config.build.env

var webpackConfig = merge(baseWebpackConfig, {
  module: {
    rules: utils.styleLoaders({
      sourceMap: config.build.productionSourceMap,
      extract: true
    })
  },
  devtool: config.build.productionSourceMap ? '#source-map' : false,
  output: {
    path: config.build.assetsRoot,
    filename: utils.assetsPath('js/[name].[chunkhash].js'),
    chunkFilename: utils.assetsPath('js/[id].[chunkhash].js')
  },
  plugins: [
    new webpack.DefinePlugin({
      'process.env': env
    }),
    new webpack.optimize.UglifyJsPlugin({
      compress: {
        warnings: false
      },
      sourceMap: true
    }),
    // extract css into its own file
    new ExtractTextPlugin({
      filename: utils.assetsPath('css/[name].[contenthash].css')
    }),
    // Compress extracted CSS. We are using this plugin so that possible
    // duplicated CSS from different components can be deduped.
    new OptimizeCSSPlugin({
      cssProcessorOptions: {
        safe: true
      }
    }),
    // 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
    new HtmlWebpackPlugin({
      filename: config.build.index,
      template: 'index.html',
      inject: true,
      minify: {
        removeComments: true,
        collapseWhitespace: true,
        removeAttributeQuotes: true
      },
      chunksSortMode: 'dependency'
    }),
    // split vendor js into its own file
    new webpack.optimize.CommonsChunkPlugin({
      name: 'vendor',
      minChunks: function (module, count) {
        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',
      chunks: ['vendor']
    }),
    // copy custom static assets
    new CopyWebpackPlugin([
      {
        from: path.resolve(__dirname, '../static'),
        to: config.build.assetsSubDirectory,
        ignore: ['.*']
      }
    ])
  ]
})

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) {
  var BundleAnalyzerPlugin = require('webpack-bundle-analyzer').BundleAnalyzerPlugin
  webpackConfig.plugins.push(new BundleAnalyzerPlugin())
}

module.exports = webpackConfig

参考

Vue 入门系列之手把手教你搭Webpack
vue-cli中的webpack配置
Vue.js学习系列四——Webpack打包工具的使用（装修中……）