多进程打包

需安装插件：thread-loader

多进程打包：
进程启动大概为600ms，进程通信也有开销
只用工作消耗时间比较长，才需要多进程打包

webpack.config.js

const { resolve } = require('path')
const MiniCssExtractPlugin = require('mini-css-extract-plugin')
const OptimizeCssAssetsWebpackPlugin = require('optimize-css-assets-webpack-plugin');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const WorkboxWebpackPlugin = require('workbox-webpack-plugin')
/*
   PWA：渐进式网络开发应用程序（离线可访问）
   workbox --> workbox-webpack-plugin
*/
 //定义nodejs环境变量：决定使用browserslist的哪个环境
process.env.NODE_ENV = 'production'
//复用loader
const commonCssLoader = [
    MiniCssExtractPlugin.loader,
    'css-loader',
    {
        //还需要在package.json中定义browserslist
        loader: 'postcss-loader',
        options: {
            ident: 'postcss',
            plugins: () => [
                require('postcss-preset-env')()
            ],
        }
    }
]
module.exports = {
    entry: './src/js/index.js',
    output: {
        filename: 'js/built.[contenthash:10].js',
        path: resolve(__dirname, 'build'),
        // publicPath: 'build'
    },
    module: {
        rules: [
            {
                //在package.json中eslintConfig --> airbnb
                test: /\.js$/,
                exclude: /node_modules/,
                //优先执行
                enforce: 'pre',
                loader: 'eslint-loader',
                options: {
                    fix: true
                }
            },
            {
                //以下loader只会匹配一个
                //注意：不能有两个配置 处理同一个文件
                oneOf: [
                    {
                        test: /\.css$/,
                        use: [...commonCssLoader],
                    },
                    {
                        test: /\.less$/,
                        use: [...commonCssLoader, 'less-loader']
                    },
                    /**
                     * 正常来讲，一个文件只能被一个loader处理
                     * 当一个文件要被多个loader处理，那么一定要指定loader执行的先后顺序：
                     * 先执行eslint 再执行babel
                     */
                    {
                        test: /\.js$/,
                        exclude: /node_modules/,
                        use:[
                            /*
                            多进程打包
                            进程启动大概为600ms，进程通信也有开销
                            只用工作消耗时间比较长，才需要多进程打包
                            */
                           {
                            loader:'thread-loader',
                            options:{
                                workers:2 //进程两个
                            }
                            },
                            {
                                loader: 'babel-loader',
                                options: {
                                    presets: [
                                        [
                                            '@babel/preset-env',
                                            {
                                                //按需加载
                                                useBuiltIns: 'usage',
                                                //指定core-js版本
                                                corejs: {
                                                    version: 3
                                                },
                                                targets: {
                                                    chrome: '60',
                                                    firefox: '60',
                                                    ie: '9',
                                                    safari: '10',
                                                    edge: '17'
                                                }
                                            }
                                        ],
                                    ],
                                    //开启babel缓存
                                    //第二次构建时，会读取之前的缓存
                                    cacheDirectory:true
                                }
                            }
                        ],
                    },
                    {
                        test: /\.(jpg|png|gif)/,
                        loader: 'url-loader',
                        options: {
                            limit: 8 * 1024,
                            name: '[hash:10].[ext]',
                            outputPath: '../imgs',
                            esModule: false,
                        }
                    },
                    {
                        test: /\.html$/,
                        loader: 'html-loader'
                    },
                    {
                        exclude: /\.(js|css|less|html|jpg|png|gif)/,
                        loader: 'file-loader',
                        options: {
                            outputPath: 'media',
                        }
                    }
                ]
            }
        ]
    },
    plugins: [
        new MiniCssExtractPlugin({
            filename: 'css/built.[contenthash:10].css'
        }),
        new OptimizeCssAssetsWebpackPlugin(),
        new HtmlWebpackPlugin({
            template: './src/index.html',
            minify: {
                collapseWhitespace: true,
                removeComments: true
            }
        }),
        new WorkboxWebpackPlugin.GenerateSW({
            /**
             * 1.帮助serviceworker快速启动
             * 2.删除旧的serviceworker
             * 
             * 生成serviceworker的配置文件
             */
            clientsClaim:true,
            skipWaiting:true
        })
    ],
    mode: 'production',
    devtool:'source-map'
}