webpack优化系列-多进程打包thread-loader

项目变的庞大，文件很多的情况下，采取多进程打包

• 如果小项目，文件不多，无需开启多进程打包，反而会变慢，因为开启进程是需要花费时间的

多进程打包：

1 安装 thread-loader
npm i thread-loader -D

配置如下：

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module.exports = {   entry: './src/js/index.js',   output: {     filename: 'js/built.[contenthash:10].js',     path: resolve(__dirname, 'build')   },   module: {     rules: [           {             test: /\.js$/,             exclude: /node_modules/,             use: [               /*                 开启多进程打包。                 进程启动大概为600ms，进程通信也有开销。                 只有工作消耗时间比较长，才需要多进程打包               */               {                 loader: 'thread-loader',                 options: {                   workers: 2 // 进程2个                 }               },               {                 loader: 'babel-loader',                 options: {                   presets: [                     [                       '@babel/preset-env',                       {                         useBuiltIns: 'usage',                         corejs: { version: 3 },                         targets: {                           chrome: '60',                           firefox: '50'                         }                       }                     ]                   ],                   // 开启babel缓存                   // 第二次构建时，会读取之前的缓存                   cacheDirectory: true                 }               }             ]           }     ]   }