Webpack：Tree Shaking（9）

介绍

Three Shaking只支持import的静态引入模块的模式，require是commonJS动态引入不支持。在production打包模式下自动被使用。

webpack.config.js

const path = require('path');
var HtmlWebpackPlugin = require('html-webpack-plugin');
const {
      CleanWebpackPlugin } = require('clean-webpack-plugin');
const webpack = require('webpack');
module.exports = {
     
    mode: 'development',
    devtool: 'cheap-module-eval-source-map',
    entry: {
     
        main: './src/index.js'
    },
    module: {
     
        rules: [
            {
     
                test: /\.js$/,
                exclude: /node_modules/,
                loader: "babel-loader"
            }
        ]
    },
    devServer: {
     
        contentBase: './dist'
    },
    plugins: [
        new HtmlWebpackPlugin({
     
            template: 'src/index.html'
        }),
        new CleanWebpackPlugin()
    ],
    optimization: {
      //development打包的模式才需要这个
        usedExports: true
    },
    output: {
     
        filename: '[name].js',
        path: path.resolve(__dirname, 'dist')
    }
};

pageck.json

配置文件的sideEffects字段，使css等配置文件不要被tree shaking掉。tree shaking会检查文件是否有导出，像css文件这种没有导出的都会被tree shaking掉。

{
     
  "name": "webpack-demo",
  "sideEffects": [
    "*.css"
  ],
  "version": "1.0.0",
  "description": "",
  "main": "webpack.config.js",
  "dependencies": {
     
    "@babel/polyfill": "^7.11.5",
    "@babel/runtime-corejs2": "^7.11.2",
    "url-loader": "^4.1.0",
    "webpack": "^4.44.2",
    "webpack-cli": "^3.3.12"
  },
  "devDependencies": {
     
    "@babel/core": "^7.11.6",
    "@babel/plugin-transform-runtime": "^7.11.5",
    "@babel/preset-env": "^7.11.5",
    "autoprefixer": "^9.8.6",
    "babel-loader": "^8.1.0",
    "clean-webpack-plugin": "^3.0.0",
    "css-loader": "^4.3.0",
    "file-loader": "^6.1.0",
    "html-webpack-plugin": "^4.5.0",
    "node-sass": "^4.14.1",
    "postcss-loader": "^4.0.2",
    "sass-loader": "^10.0.2",
    "style-loader": "^1.2.1",
    "webpack-dev-server": "^3.11.0"
  },
  "scripts": {
     
    "watch": "webpack --watch",
    "start": "webpack-dev-server --open",
    "boundle": "webpack"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "browserslist": [
    "> 1%",
    "last 2 versions",
    "not ie <= 8"
  ]
}