背景
最近有感觉到，随着系统模块数量的增加，wepack编译打包的速度越来越慢，于是我想给项目做一下优化升级，也借此机会系统地学习一下webpack4。
升级过程
当前版本
"dependencies": {
"@fullcalendar/core": "^4.2.0",
"@fullcalendar/daygrid": "^4.2.0",
"@fullcalendar/interaction": "^4.2.0",
"@fullcalendar/vue": "^4.2.2",
"axios": "0.18.1",
"babel-polyfill": "6.26.0",
"echarts": "4.0.4",
"element-ui": "2.10.0",
"jquery": "3.3.1",
"js-cookie": "2.2.0",
"js-md5": "0.7.3",
"lodash": "4.17.5",
"moment": "^2.24.0",
"node-sass": "^4.11.0",
"normalize.css": "7.0.0",
"nprogress": "0.2.0",
"qs": "6.5.1",
"vue": "2.6.10",
"vue-router": "3.0.3",
"vuex": "3.1.1"
},
"devDependencies": {
"autoprefixer": "7.2.3",
"babel-core": "6.26.0",
"babel-eslint": "8.0.3",
"babel-helper-vue-jsx-merge-props": "2.0.3",
"babel-loader": "7.1.2",
"babel-plugin-syntax-jsx": "6.18.0",
"babel-plugin-transform-runtime": "6.23.0",
"babel-plugin-transform-vue-jsx": "3.7.0",
"babel-preset-env": "1.6.1",
"babel-preset-stage-2": "6.24.1",
"chalk": "2.3.0",
"copy-webpack-plugin": "4.2.3",
"css-loader": "0.28.7",
"eslint": "4.13.1",
"eslint-friendly-formatter": "3.0.0",
"eslint-loader": "1.9.0",
"eslint-plugin-html": "4.0.1",
"eventsource-polyfill": "0.9.6",
"extract-text-webpack-plugin": "3.0.2",
"file-loader": "1.1.5",
"friendly-errors-webpack-plugin": "1.6.1",
"html-webpack-plugin": "2.30.1",
"node-notifier": "5.1.2",
"optimize-css-assets-webpack-plugin": "3.2.0",
"ora": "1.3.0",
"portfinder": "1.0.13",
"postcss-import": "11.0.0",
"postcss-loader": "2.0.9",
"rimraf": "2.6.2",
"sass-loader": "6.0.6",
"semver": "5.4.1",
"shelljs": "0.7.8",
"svg-sprite-loader": "4.1.6",
"uglifyjs-webpack-plugin": "1.1.3",
"url-loader": "0.6.2",
"vue-loader": "15.7.0",
"vue-style-loader": "4.1.2",
"vue-template-compiler": "2.6.10",
"webpack": "3.10.0",
"webpack-bundle-analyzer": "2.9.1",
"webpack-dev-server": "2.9.7",
"webpack-merge": "4.1.1"
}
目标版本
"dependencies": {
"@fullcalendar/core": "^4.2.0",
"@fullcalendar/daygrid": "^4.2.0",
"@fullcalendar/interaction": "^4.2.0",
"@fullcalendar/vue": "^4.2.2",
"axios": "0.18.1",
"babel-polyfill": "6.26.0",
"echarts": "4.0.4",
"element-ui": "2.10.0",
"jquery": "3.3.1",
"js-cookie": "2.2.0",
"js-md5": "0.7.3",
"lodash": "4.17.5",
"moment": "^2.24.0",
"node-sass": "^4.11.0",
"normalize.css": "7.0.0",
"nprogress": "0.2.0",
"qs": "6.5.1",
"vue": "2.6.10",
"vue-router": "3.0.3",
"vuex": "3.1.1"
},
"devDependencies": {
"autoprefixer": "9.6.1",
"babel-core": "6.26.3",
"babel-eslint": "10.0.3",
"babel-helper-vue-jsx-merge-props": "2.0.3",
"babel-loader": "^7.1.5",
"babel-plugin-syntax-jsx": "6.18.0",
"babel-plugin-transform-runtime": "6.23.0",
"babel-plugin-transform-vue-jsx": "3.7.0",
"babel-preset-env": "1.7.0",
"babel-preset-stage-2": "6.24.1",
"chalk": "2.4.2",
"copy-webpack-plugin": "5.0.4",
"css-loader": "3.2.0",
"eslint": "6.3.0",
"eslint-friendly-formatter": "3.0.0",
"eslint-import-resolver-webpack": "^0.11.1",
"eslint-loader": "3.0.0",
"eslint-plugin-vue": "^5.2.3",
"eventsource-polyfill": "0.9.6",
"file-loader": "4.2.0",
"friendly-errors-webpack-plugin": "1.7.0",
"html-webpack-plugin": "3.2.0",
"mini-css-extract-plugin": "^0.8.0",
"node-notifier": "5.1.2",
"optimize-css-assets-webpack-plugin": "3.2.0",
"ora": "1.3.0",
"portfinder": "1.0.13",
"postcss-import": "12.0.1",
"postcss-loader": "3.0.0",
"rimraf": "2.6.2",
"sass-loader": "8.0.0",
"semver": "5.4.1",
"shelljs": "0.7.8",
"svg-sprite-loader": "4.1.6",
"uglifyjs-webpack-plugin": "2.2.0",
"url-loader": "2.1.0",
"vue-loader": "15.7.1",
"vue-style-loader": "4.1.2",
"vue-template-compiler": "2.6.10",
"webpack": "4.39.3",
"webpack-bundle-analyzer": "3.4.1",
"webpack-cli": "^3.3.8",
"webpack-dev-server": "3.8.0",
"webpack-merge": "4.2.2"
}
第一步
升级webpack到4.39.3版本，npm run dev遇到了报错......
npm run dev报错
webpack-dev-server版本过低
Error: Cannot find module 'webpack/bin/config-yargs'
应该是webpack与webpack-dev-server版本不符，于是升级webpack-dev-server到3.8.0版本。
webpack-cli缺失
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 i -D webpack-cli
-> When using yarn: yarn add -D webpack-cli
internal/modules/cjs/loader.js:584
throw err;
^
Error: Cannot find module 'webpack-cli/bin/config-yargs'
webpack4将webpack-cli单独分离出来了，因此提示我们安装webpack-cli，那就直接安装吧。
html-webpack-plugin版本问题
10% building 2/2 modules 0 active(node:8596) DeprecationWarning: Tapable.plugin is deprecated. Use new API on `.hooks` instead
(node:8596) DeprecationWarning: Tapable.apply is deprecated. Call apply on the plugin directly instead
53% building 363/366 modules 3 active D:coolluprojectscoollu-v3source-codedevelopcoollu-cloud-web
ode_modulescore-jsmodules\_array-reduce.jsD:coolluprojectscoollu-v3source-codedevelopcoollu-cloud-web
ode_moduleshtml-webpack-pluginlibcompiler.js:81
var outputName = compilation.mainTemplate.applyPluginsWaterfall('asset-path', outputOptions.filename, {
^
TypeError: compilation.mainTemplate.applyPluginsWaterfall is not a function
考虑是html-webpack-plugin版本问题，升级至3.2.0
extract-text-webpack-plugin?
10% building 2/2 modules 0 active(node:19732) DeprecationWarning: Tapable.plugin is deprecated. Use new API on `.hooks` instead
查到是因为extract-text-webpack-plugin不再支持webpack4.3，需要改用mini-css-extract-plugin。
ps: extract-text-webpack-plugin是用来抽取依赖的.css文件的，防止样式全部打包在js bundle里太大。改用了mini-css-extract-plugin后，该报错并未消除，考虑要用compiler钩子重写一些东西，先在这埋个坑，后面弄明白了再来填坑。
eslint-loader升版本
Module build failed (from ./node_modules/eslint-loader/index.js):
TypeError: Cannot read property 'eslint' of undefined
at Object.module.exports (D:coolluprojectscoollu-v3source-codedevelopcoollu-cloud-web
ode_moduleseslint-loaderindex.js:148:18)
升级eslint-loader
file-loader升版本
Module build failed (from ./node_modules/file-loader/dist/cjs.js):
TypeError: Cannot read property 'context' of undefined
at Object.loader (D:coolluprojectscoollu-v3source-codedevelopcoollu-cloud-web
ode_modulesfile-loaderdistindex.js:34:49)
升级file-loader
npm run build报错
改用splitChunks
webpack.optimize.CommonsChunkPlugin has been removed, please use config.optimization.splitChunks instead.
使用webpack4的optimization.splitChunks替代CommonsChunkPlugin
vue-loader升版本
ERROR in ./src/App.vue?vue&type=style&index=0&id=7c362b6c&lang=scss&scoped=tr (./node_modules/mini-css-extract-plugin/dist/loader.js??ref--10-0!./node_mods/vue-loader/lib??vue-loader-options!./src/App.vue?vue&type=style&index=0&id=62b6c&lang=scss&scoped=true&)
Module build failed (from ./node_modules/mini-css-extract-plugin/dist/loader.:
ModuleParseError: Module parse failed: Unexpected character '#' (14:0)
File was processed with these loaders:
* ./node_modules/vue-loader/lib/index.js
You may need an additional loader to handle the result of these loaders.
考虑是vue-loader版本问题，先升级vue-loader@15.7.1
babel-loader降版本
ERROR in ./src/main.js
Module build failed (from ./node_modules/babel-loader/lib/index.js):
Error: Cannot find module '@babel/core'
babel-loader@8 requires Babel 7.x (the package '@babel/core'). If you'd like to use Babel 6.x ('babel-core'), you should install 'babel-loader@7'.
把babel-loader@8降低了版本，调整为babel-loader@7
ps: 想了一下，觉得可能其他的loader版本也会过低，于是将其他的loader都进行了升级，具体见package.json。
优化打包速度
happypack
一个号称用多进程策略提升webpack打包速度的插件，真的挺管用的。
happypack允许您并行转换多个文件，从而加快了webpack的构建速度。
安装：
npm install --save-dev happypack
简单配置如下：
const HappyPack = require('happypack')
// webpack配置，只列出关于happypack的配置
rules: [
// ...其他rule
{
test: /.js$/,
// 注释掉原来的babel-loader，改用happypack/loader
// loader: "babel-loader",
use: ['happypack/loader'],
include: [
resolve("src")
]
}
],
plugins: [
// ...其他plugin
// 安装说明简单配置了一下
new HappyPack({
// 将我们刚才注释的loader放在这，告诉happypack
loaders: ['babel-loader'],
// 开启4个子进程，据说是最优解
threads: 4
})
]
总结
经过大量npm包版本的调整，以及webpack配置的修改（主要是optimization的调整；把extract-text-webpack-plugin换成了mini-css-extract-plugin；加入了happypack），报错基本上消除了，经测试，dev和prod环境都没有功能上的问题，热加载，编译，打包速度确实得到了显著提升。
-
热加载
速度得到了显著提升，之前改一行代码，热加载编译的时间差不多要花
1min，让人难受；优化后，基本上控制在<=5s -
webpack升级前打包：Hash: 35f207120dd3736758dd Version: webpack 3.10.0 Time: 95987ms大概需要
96s的打包时间。 -
webpack升级后打包：Hash: fb73468076752cad58f6 Version: webpack 4.39.3 Time: 61597ms打包时间降低到
61.6s，节约了34.4s，打包效率提升了35.8%以上。 -
使用
happypack后：Happy[1]: Version: 5.0.1. Threads: 4 Happy[1]: All set; signaling webpack to proceed. Hash: a635e8b39b7064adf41c Version: webpack 4.39.3 Time: 41047ms打包时间降低到
41s，再次节约了20.6s！总共节约了55s，与升级前相比，打包效率提升了57%以上。
当然可优化的空间还很大，webpack4还有很多东西值得我们去折腾，优化之路还在继续！
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