vue脚手架初始化项目中配置文件webpack.prod.conf.js代码含义

'use strict'
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')

const webpackConfig = merge(baseWebpackConfig, {
  module: {
    rules: utils.styleLoaders({
      sourceMap: config.build.productionSourceMap,
      extract: true,
      usePostCSS: true
    })
  },
  devtool: config.build.productionSourceMap ? config.build.devtool : false,
  //最终生成的路径都是基于output.path
  output: {
    path: config.build.assetsRoot,
    // 编译输出文件名格式
    filename: utils.assetsPath('js/[name].[chunkhash].js'),
    // 没有指定输出名的文件输出的文件名格式
    chunkFilename: utils.assetsPath('js/[id].[chunkhash].js')
  },
  plugins: [
    new webpack.DefinePlugin({
      'process.env': env//生产环境下
    }),
    new UglifyJsPlugin({//压缩代码
      uglifyOptions: {
        compress: {
          warnings: false
        }
      },
      sourceMap: config.build.productionSourceMap,
      parallel: true
    }),
    //提取css文件
    new ExtractTextPlugin({
      filename: utils.assetsPath('css/[name].[contenthash].css'),
      allChunks: true,//设置为“false”时，不会提取CSS。CSS将被webpack使用style-loader动态加载。
    }),
    //压缩提取的CSS文件，删除不同组件中重复的CSS代码。
    new OptimizeCSSPlugin({
      cssProcessorOptions: config.build.productionSourceMap
        ? { safe: true, map: { inline: false } }
        : { safe: true }
    }),

    //以src/index.html为模板，将打包后的结果，自动引入到html中并产出到dist目录下。
    new HtmlWebpackPlugin({
      filename: config.build.index,
      template: 'index.html',
      inject: true,
      minify: {
        removeComments: true,
        collapseWhitespace: true,
        removeAttributeQuotes: true
      },
      chunksSortMode: 'dependency'
    }),
    new webpack.HashedModuleIdsPlugin(),
    new webpack.optimize.ModuleConcatenationPlugin(),

    //多入口文件，可能存在重复代码，把公共代码分类提取到不同的文件
    // CommonsChunkPlugin初始化常用参数？
    // 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
    new webpack.optimize.CommonsChunkPlugin({
      //位于node_modules中的必需的第三方模块将被提取到vendor.js文件。
      name: 'vendor',
      minChunks (module) {
        return (
          module.resource &&
          /\.js$/.test(module.resource) &&
          module.resource.indexOf(
            path.join(__dirname, '../node_modules')
          ) === 0
        )
      }
    }),
    new webpack.optimize.CommonsChunkPlugin({
      // webpack runtime and module manifest 将被提取到manifest.js文件。
      name: 'manifest',
      minChunks: Infinity
    }),
    new webpack.optimize.CommonsChunkPlugin({
      //其它公共代码提取到app.js中
      name: 'app',
      async: 'vendor-async',
      children: true,
      minChunks: 3
    }),

    // copy custom static assets
    new CopyWebpackPlugin([
      {
        from: path.resolve(__dirname, '../static'),
        to: config.build.assetsSubDirectory,
        ignore: ['.*']
      }
    ])
  ]
})

// gzip模式下引入compression插件进行压缩
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
    })
  )
}

if (config.build.bundleAnalyzerReport) {
  const BundleAnalyzerPlugin = require('webpack-bundle-analyzer').BundleAnalyzerPlugin
  webpackConfig.plugins.push(new BundleAnalyzerPlugin())
}

module.exports = webpackConfig