Webpack4 性能优化实践

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发声的沉默者

修改于 2021-06-16 10:04:55

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修改于 2021-06-16 10:04:55

为什么需要性能优化

在使用 Webpack 时，如果不注意性能优化，可能会产生性能问题，会导致在开发体验上不是非常丝滑，性能问题主要是编译速度慢，打包体积过大，因此性能优化也主要从这些方面来分析。本文主要是自己平时的工作积累和参考别人的文章，而进行总结，基于 Webpack4 版本。

构建分析

编译速度分析

对 Webpack 构建速度进行优化的首要任务就是去知道哪些地方值得我们注意。

speed-measure-webpack-plugin 插件能够测量 Webpack 构建速度

 SMP  ⏱

General output time took 38.3 secs



 SMP  ⏱  Plugins

HtmlWebpackPlugin took 1.31 secs

CopyPlugin took 0.016 secs

OptimizeCssAssetsWebpackPlugin took 0.002 secs

ContextReplacementPlugin took 0.001 secs

MiniCssExtractPlugin took 0 secs

DefinePlugin took 0 secs



 SMP  ⏱  Loaders

\_babel-loader@8.1.0@babel-loader took 29.98 secs

  module count = 1503

\_babel-loader@8.1.0@babel-loader, and

\_eslint-loader@3.0.4@eslint-loader took 18.74 secs

  module count = 86

\_css-loader@3.6.0@css-loader, and

\_less-loader@5.0.0@less-loader took 16.45 secs

  module count = 64

modules with no loaders took 2.24 secs

  module count = 7

\_file-loader@5.1.0@file-loader took 1.03 secs

  module count = 17

\_style-loader@1.3.0@style-loader, and

\_css-loader@3.6.0@css-loader, and

\_less-loader@5.0.0@less-loader took 0.102 secs

  module count = 64

\_html-webpack-plugin@3.2.0@html-webpack-plugin took 0.021 secs

  module count = 1

居然达到了惊人的 **38.3** 秒，虽然有点不是很准确，但是非常慢。发现 babel-loader、eslint-loader、css-loader、less-loader 占据了大头。

const webpackBase = require('./webpack.base.conf');

const path = require('path');



const SpeedMeasureWebpackPlugin = require('speed-measure-webpack-plugin');

const smp = new SpeedMeasureWebpackPlugin();



module.exports = smp.wrap({

    // 配置源码显示方式

    devtool: 'eval-source-map',

    mode: 'development',

    entry: {

        app: ['./src/index.jsx']

    },

    output: {

        path: path.resolve(\_\_dirname, 'dist'),

        filename: 'index.js'

    },

    resolve: webpackBase.resolve,

    module: webpackBase.module,

    stats: webpackBase.stats,

    optimization: webpackBase.optimization,

    plugins: [

        webpackBase.plugins.html,

        webpackBase.plugins.miniCssExtract,

        webpackBase.plugins.optimizeCssAssets,

        // webpackBase.plugins.progressBarPlugin,

        webpackBase.plugins.ContextReplacementPlugin,

        webpackBase.plugins.DefinePlugin,

        // webpackBase.plugins.AntdDayjsWebpackPlugin,

        webpackBase.plugins.CopyPlugin

        // webpackBase.plugins.HotModuleReplacementPlugin

    ],

    devServer: webpackBase.devServer,

    watchOptions: webpackBase.watchOptions,

    externals: webpackBase.externals

});

打包体积分析

通过 webpack-bundle-analyzer 插件能够在 Webpack 构建结束后生成构建产物体积报告，配合可视化的页面，能够直观知道产物中的具体占用体积。

const BundleAnalyzerPlugin = require('webpack-bundle-analyzer').BundleAnalyzerPlugin;

module.exports = {

  plugins: bundleAnalyzer: new BundleAnalyzerPlugin({ analyzerPort: 8081 })],

};

效果图如下：

可以看出一个很明显的问题就是 Ant Design、TRTC、Mobx 这些库，没有排除。

打包体积如下：

如何优化

缩小构建目标

优化 resolve.modules 配置（减少模块搜索层级和不必要的编译工作）
优化 resolve.extensions 配置
增加缓存

const path = require('path');

module.exports = {

    resolve: {

        // 自动解析确定的扩展

        extensions: ['.js', '.jsx', '.css', '.less', '.json'],

        alias: {

            // 创建 import 或 require 的别名，来确保模块引入变得更简单

            'react': path.resolve( \_\_dirname ,'./node\_modules/react/dist/react.min.js')

        },

        // 当从 npm 包导入模块时，此选项将决定在 `package.json` 中使用哪个字段导入模块

        // 默认值为 browser -> module -> main

        mainFields: ['main']

    },

    module: {

        rules: [

            {

                // 排除node\_modules模块

                test: /\.(js|jsx)$/,

                exclude: /node\_modules/,

                // 开启缓存

                loader: 'babel-loader?cacheDirectory=true'

            }

        ]

    }

};

使用 thread-loader，开启多进程

thread-loader 会将你的 loader 放置在一个 worker 池里面运行，每个 worker 都是一个单独的有 **600ms** 限制的 node.js 进程。同时跨进程的数据交换也会被限制。请在高开销的 loader 中使用，否则效果不佳。

module.exports = {

  module: {

    rules: [

      {

        test: /\.js$/,

        include: path.resolve('src'),

        use: [

          'thread-loader',

          // your expensive loader (e.g babel-loader)

        ],

      },

    ],

  },

};

使用 hard-source-webpack-plugin

在 Webpack4 中，hard-source-webpack-plugin 是 DLL 的更好替代者。

hard-source-webpack-plugin 是 Webpack 的插件，为模块提供中间缓存步骤。为了查看结果，您需要使用此插件运行 Webpack 两次：第一次构建将花费正常的时间。第二次构建将显着加快（大概提升 **90%** 的构建速度）。不过该插件很久没更新了，不太建议使用。

去掉 eslint-loade

由于我项目中使用了 eslint-loader 如果配置了 precommit，其实可以去掉的。

通过 externals 把相关的包，排除

Webpack

module.exports = {

    // externals 排除对应的包，注：排除掉的包必须要用script标签引入下

    externals: {

        react: 'React',

        'react-dom': 'ReactDOM',

        'trtc-js-sdk': 'TRTC',

        bizcharts: 'BizCharts',

        antd: 'antd',

        mobx: 'mobx',

        'mobx-react': 'mobxReact'

    }

};

index.html

<!DOCTYPE html>

<html lang="zh">

    <head>

        <meta charset="utf-8" />

        <meta

            name="viewport"

            content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=0"

        />

        <meta name="baidu-site-verification" content="ptk9VJudKz" />

        <link

            rel="stylesheet"

            href="https://xxx/antd.min3.26.20.css"

        />

        <title>webpack</title>

        <script

            type="text/javascript"

            src="https://xxx/17.0.0react.production.min.js"

        ></script>

        <script

            type="text/javascript"

            src="https://xxx/17.0.0react-dom.production.min.js"

        ></script>

        <script

            type="text/javascript"

            src="https://xxx/BizCharts3.5.8.js"

        ></script>

        <script

            type="text/javascript"

            src="https://xxx/trtc4.6.7.js"

        ></script>

        <script

            type="text/javascript"

            src="https://xxx/moment2.29.1.min.js"

        ></script>

        <script

            type="text/javascript"

            src="https://xxx/moment2.29.1zh-cn.js"

        ></script>

        <script

            type="text/javascript"

            src="https://xxx/polyfill.min7.8.0.js"

        ></script>

        <script

            type="text/javascript"

            src="https://xxx/antd.min3.26.20.js"

        ></script>

        <script

            type="text/javascript"

            src="https://xxx/mobx.umd.min5.13.1.js"

        ></script>

        <script

            type="text/javascript"

            src="https://xxx/mobx-react.index.min5.4.4.js"

        ></script>

    </head>

    <body>

        <div id="root"></div>

    </body>

</html>

JS 压缩

从 Webpack4 开始，默认情况下使用 terser 压缩生产环境下的输出结果。Terser 是一款兼容 ES2015 + 的 JavaScript 压缩器。与 UglifyJS（许多项目的早期标准）相比，它是面向未来的选择。有一个 UglifyJS 的分支—— uglify-es，但由于它不再维护，于是就从这个分支诞生出了一个独立分支，它就是 terser。

const TerserPlugin = require('terser-webpack-plugin');



module.exports = {

    optimization: {

        minimizer: [

            // 压缩js

            new TerserPlugin({

                test: /\.(jsx|js)$/,

                extractComments: true,

                parallel: true,

                cache: true

            })

        ]

    },

};

CSS 压缩

Webpack 4.0 以后，官方推荐使用 mini-css-extract-plugin 插件来打包 CSS 文件。

const MiniCssExtractPlugin = require('mini-css-extract-plugin');



module.exports = {

    module: {

        rules: [

            {

                test: /\.(css|less)$/,

                use: [MiniCssExtractPlugin.loader]

            }

        ]

    },

};

FAQ

Ant Design 无法加载

请确保加载顺序，Moment、Polyfill 放在 Ant Design 前面加载

MobX 无法加载

MobX 引入 mobx.umd.min.js 库，mobx-react 需要引入

package.json

{

    "name": "webpack",

    "version": "1.0.0",

    "private": true,

    "main": "index.js",

    "dependencies": {

        "antd": "^3.26.20",

        "babel-eslint": "^10.0.3",

        "babel-loader": "^8.0.0",

        "babel-plugin-import": "^1.13.0",

        "babel-plugin-react-css-modules": "^5.2.6",

        "bizcharts": "^3.5.8",

        "china-division": "^2.3.1",

        "compression-webpack-plugin": "^3.0.1",

        "copy-webpack-plugin": "^5.1.1",

        "css-loader": "^3.2.0",

        "eslint": "^6.8.0",

        "eslint-config-prettier": "^6.11.0",

        "eslint-config-standard": "^14.1.0",

        "eslint-loader": "^3.0.4",

        "eslint-plugin-import": "^2.20.0",

        "eslint-plugin-promise": "^4.2.1",

        "eslint-plugin-react": "^7.17.0",

        "eslint-plugin-standard": "^4.0.1",

        "html-webpack-plugin": "^3.2.0",

        "less": "^3.8.1",

        "less-loader": "^5.0.0",

        "lint-staged": "^10.0.8",

        "mini-css-extract-plugin": "^0.8.0",

        "mobx": "^5.13.1",

        "mobx-react": "^5.4.4",

        "optimize-css-assets-webpack-plugin": "^5.0.1",

        "pre-commit": "^1.2.2",

        "progress-bar-webpack-plugin": "^1.12.1",

        "react": "^17.0.0",

        "react-dom": "^17.0.0",

        "speed-measure-webpack-plugin": "^1.3.1",

        "style-loader": "^1.2.1",

        "terser-webpack-plugin": "^2.2.1",

        "trtc-js-sdk": "^4.6.7",

        "viewerjs": "^1.5.0",

        "webpack": "^4.41.2",

        "webpack-bundle-analyzer": "^3.6.0",

        "webpack-cli": "^3.3.10",

        "webpack-dev-server": "^3.10.1"

    }

}

最终效果

打包体积：

打包体积由原先 **2.1M** 变成了 **882KB**，可以说效果非常巨大。

包依赖：

Ant Design、TRTC、Mobx 这些库也没了

编译速度：

SMP  ⏱

General output time took 10.67 secs



 SMP  ⏱  Plugins

HtmlWebpackPlugin took 1.69 secs

BundleAnalyzerPlugin took 0.091 secs

CopyPlugin took 0.011 secs

MiniCssExtractPlugin took 0.003 secs

OptimizeCssAssetsWebpackPlugin took 0.002 secs

DefinePlugin took 0.001 secs

ContextReplacementPlugin took 0 secs



 SMP  ⏱  Loaders

\_babel-loader@8.1.0@babel-loader took 8.26 secs

  module count = 277

\_babel-loader@8.1.0@babel-loader, and

\_eslint-loader@3.0.4@eslint-loader took 7.18 secs

  module count = 86

\_css-loader@3.6.0@css-loader, and

\_less-loader@5.0.0@less-loader took 1.94 secs

  module count = 28

modules with no loaders took 0.728 secs

  module count = 12

\_file-loader@5.1.0@file-loader took 0.392 secs

  module count = 17

\_style-loader@1.3.0@style-loader, and

\_css-loader@3.6.0@css-loader, and

\_less-loader@5.0.0@less-loader took 0.052 secs

  module count = 28

\_html-webpack-plugin@3.2.0@html-webpack-plugin took 0.026 secs

  module count = 1

编译速度由原先 **38.3 secs**（实际编译速度大概 15 秒左右），减少到 **10.67 secs**（实际编译速度 10 秒左右）。

国内外公共 CDN 地址

参考资料

博客

原创声明：本文系作者授权腾讯云开发者社区发表，未经许可，不得转载。

如有侵权，请联系 cloudcommunity@tencent.com 删除。

webpack

react

vue.js

原创声明：本文系作者授权腾讯云开发者社区发表，未经许可，不得转载。

如有侵权，请联系 cloudcommunity@tencent.com 删除。

webpack

react

vue.js

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