Webpack4性能优化实践

发声的沉默者 2020-11-13 11:00:59
优化 性能 webpack webpack4 实践


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:

5061604735941_ pic_hd

可以看出一个很明显的问题就是 ant、trtc、mobx 这些库,没有排除。

打包体积如下:

image

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-loader

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 无法加载

请确保加载顺序,moment、polyfill 放在 ant 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:

5381605008681_ pic

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:

5441605062491_ pic_hd

ant、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)。

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版权声明
本文为[发声的沉默者]所创,转载请带上原文链接,感谢
https://segmentfault.com/a/1190000038156662

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