记一次webpack3升级webpack4的踩坑经历

webpack4版本也出了很久了 之前弄过一段时间的升级 后面因为种种原因搁浅了 今天有硬着头皮升级了一波 yeah 还好升级成功了

先贴一波原先webpack3的github配置

ps（我只是一个菜鸡= = webpack的配置很辣鸡 ）废话少说 开撸

1 webpack升级到4.0版本并且安装webpack-cli

yarn add webpack-cli global<br>yarn add webpack-cli -D

如果不对webpack-cli进行安装的话会报错 如下：

The CLI moved into a separate package:webpack-cli.
Please install 'webpack-cli' in addition to webpack itself to use the CLI.
->when using npm: npm install webpack-cli -D
->when using yarn: yarn add webpack-cli -D

2 对一些包的相关依赖

继续yarn run dev yeah!!! 报错了

Error: Cannot find module 'webpack/bin/config-yargs'
at Function.Module._resolveFilename (module.js:538:15)
at Function.Module._load (module.js:468:25)
at Module.require (module.js:587:17)
at require (internal/module.js:11:18)
at Object.<anonymous> (C:\Users\hboxs022\Desktop\webpack-demo\webpack-demo\node_modules\webpack-dev-server\bin\webpack-dev-server.js:54:1)
at Module._compile (module.js:643:30)
at Object.Module._extensions..js (module.js:654:10)
at Module.load (module.js:556:32)
at tryModuleLoad (module.js:499:12)
at Function.Module._load (module.js:491:3)
error Command failed with exit code 1.

解决办法：这个就是目前版本的webpack-dev-server不支持webpack4 升级一波

yarn add webpack-dev-server@3.1.1 -D //我装的是3.1.1的包

不过看了挺多资料 只要webpack-dev-server是3.0版本以上好像就兼容 大雾 反正我是3.0.0-alpha6通过了

3 去除commonchunk plugin 改用webpack.optimize.SplitChunksPlugin

再一次执行yarn run dev 然后又出错了 心里一万个奔腾的野马 没办法啊 硬着头皮看呗

出错原因

Error: webpack.optimize.CommonsChunkPlugin has been removed, please use config.optimization.splitChunks instead

webpack4废除了很多api 之前配置拆分公共代码 打包第三方库贼麻烦 然后官方一不做二不休直接废除了之前的又捣鼓了这个webpack.optimize.SplitChunksPlugin

然后关于这个插件的使用我也是弄了很久后面跑去官方的example里面去看了一下才有所头绪，如果你之前大致了解原来的commonchunk plugin直接去看官方的例子你就懂了 这里贴一下官方的example链接，其中最重要的就是关于如何打包多文件入口的common-chunk-add-vendor-chunk例子，不多说放链接直接明了的告诉你如何拆分公用代码以及第三方库。

至于打包runtime代码 webpack4直接调用新的方法 ok 完事

 new webpack.optimize.RuntimeChunkPlugin({
      name: "manifest"
    }),

关于webpack.optimize.SplitChunksPlugin的详细用法 我也贴出来 有兴趣的同学可以自己琢磨

new webpack.optimize.SplitChunksPlugin({
          chunks: "initial", // 必须三选一： "initial" | "all"(默认就是all) | "async"
          minSize: 0, // 最小尺寸，默认0
          minChunks: 1, // 最小 chunk ，默认1
          maxAsyncRequests: 1, // 最大异步请求数， 默认1
          maxInitialRequests: 1, // 最大初始化请求书，默认1
          name: function () {
          }, // 名称，此选项可接收 function
          cacheGroups: { // 这里开始设置缓存的 chunks
            priority: 0, // 缓存组优先级
            vendor: { // key 为entry中定义的 入口名称
              chunks: "initial", // 必须三选一： "initial" | "all" | "async"(默认就是异步)
              name: "vendor", // 要缓存的 分隔出来的 chunk 名称
              minSize: 0,
              minChunks: 1,
              enforce: true,
              maxAsyncRequests: 1, // 最大异步请求数， 默认1
              maxInitialRequests: 1, // 最大初始化请求书，默认1
              reuseExistingChunk: true // 可设置是否重用该chunk（查看源码没有发现默认值）
            }
          }
        }),

最后贴上修改后的webpack.optimize.SplitChunksPlugin的代码

new webpack.optimize.SplitChunksPlugin({
      cacheGroups: {
        default: {
          minChunks: 2,
          priority: -20,
          reuseExistingChunk: true,
        },
        //打包重复出现的代码
        vendor: {
          chunks: 'initial',
          minChunks: 2,
          maxInitialRequests: 5, // The default limit is too small to showcase the effect
          minSize: 0, // This is example is too small to create commons chunks
          name: 'vendor'
        },
        //打包第三方类库
        commons: {
          name: "commons",
          chunks: "initial",
          minChunks: Infinity
        }
      }
    }),

    new webpack.optimize.RuntimeChunkPlugin({
      name: "manifest"
    }),

4 升级happypack插件！！！！！

至于为啥用红字 如果使用了happypack进行多线程加速打包的小伙伴们千万要记住升级happypack 因为我卡在这里开了很久后面看了别人的配置才知道happypack也不兼容需要进行升级 泪奔。。。。贴一下当时的错误提示

TypeError: Cannot read property 'length' of undefined
at resolveLoader (C:\Users\hboxs022\Desktop\webpack-demo\webpack-demo\node_modules\happypack\lib\WebpackUtils.js:138:17)
at C:\Users\hboxs022\Desktop\webpack-demo\webpack-demo\node_modules\happypack\lib\WebpackUtils.js:126:7
at C:\Users\hboxs022\Desktop\webpack-demo\webpack-demo\node_modules\happypack\node_modules\async\lib\async.js:713:13

解决办法：升级呗

5 剩下的问题大部分都是因为当前的包与webpack4不兼容 这里就直接贴出来了

var outputName = compilation.mainTemplate.applyPluginsWaterfall('asset-path', outputOptions.filename, {
^

TypeError: compilation.mainTemplate.applyPluginsWaterfall is not a function
at C:\Users\hboxs022\Desktop\webpack-demo\webpack-demo\node_modules\html-webpack-plugin\lib\compiler.js:81:51
at compile (C:\Users\hboxs022\Desktop\webpack-demo\webpack-demo\node_modules\webpack\lib\Compiler.js:240:11)
at hooks.afterCompile.callAsync.err (C:\Users\hboxs022\Desktop\webpack-demo\webpack-demo\node_modules\webpack\lib\Compiler.js:488:14)解决办法：升级html-webpack-plugin

yarn add webpack-contrib/html-webpack-plugin -D

最后 extract-text-webpack-plugin和sass-loader也需要进行升级 具体我会在最后贴出我的webpack4 demo 大家看着安装哈

6 最后 配置完成测试一哈　　

开发环境下

yarn run start ok 效果没问题 看一下构建时间9891ms 对比图中的webpack3 17161ms

:\Users\hboxs022\Desktop\webpack4>yarn run dev
yarn run v1.3.2
$ set NODE_ENV=dev && webpack-dev-server
Happy[js]: Version: 5.0.0-beta.3. Threads: 6 (shared pool)
(node:2060) DeprecationWarning: Tapable.plugin is deprecated. Use new API on `.hooks` instead
i ｢wds｣: Project is running at http://localhost:8072/
i ｢wds｣: webpack output is served from /
i ｢wds｣: Content not from webpack is served from C:\Users\hboxs022\Desktop\webpack4\src
Happy[js]: All set; signaling webpack to proceed.
Happy[css]: Version: 5.0.0-beta.3. Threads: 6 (shared pool)
Happy[css]: All set; signaling webpack to proceed.
(node:2060) DeprecationWarning: Tapable.apply is deprecated. Call apply on the plugin directly instead
i ｢wdm｣: wait until bundle finished: /page/index.html
i ｢wdm｣: Hash: 1911cfc871cd5dc27aca
Version: webpack 4.1.1
Time: 9891ms
Built at: 2018-3-28 18:49:25

生产环境下

yarn run build

ok 第三方库jquery打包到common里了 公共js代码打包进vendor 公共样式也打包进ventor后面分离成vendor.css

目录结构也没问题 模块id也进行了固定

下面再来看看速度对比

webpack3

webpack4 是我错觉吗= =

最后贴上webpack4的github链接