// package.json
{
  "name": "WEBPACK-DEV-1",
  "version": "1.0.0",
  "main": "index.js",
  "license": "MIT",
  "scripts": {
    "dev": "webpack-dev-server",
    "build": "webpack --config webpack.config.js"
  },
  "devDependencies": {
    "@babel/core": "^7.14.6",
    "@babel/preset-env": "^7.14.5",
    "autoprefixer": "^8.0.0",
    "babel-loader": "^8.2.2",
    "css-loader": "^5.2.6",
    "expose-loader": "0.7.5",
    "html-webpack-plugin": "^4.2.1",
    "less": "^4.1.1",
    "less-loader": "^6.1.0",
    "mini-css-extract-plugin": "^1.6.0",
    "optimize-css-assets-webpack-plugin": "^4.0.0",
    "postcss-loader": "^4.0.4",
    "style-loader": "^2.0.0",
    "uglifyjs-webpack-plugin": "^2.2.0",
    "webpack": "^4.28.2",
    "webpack-cli": "^3.1.2",
    "webpack-dev-server": "^3.11.2"
  },
  "dependencies": {
    "jquery": "^3.6.0"
  }
}

// webpack.config.js

{
　　test: require.resolve(‘jquery‘),
　　use:‘expose-loader?$‘
},

// index.js
var $ = require("jquery");
console.log(‘$,‘,$)
// expore-loader 暴露 全局的loader 内联的loader
// loader[pre:前面执行的loader,normal:普通的loader,liader:内联的loader,postloader:后置loader]
// 问:什么叫做内联的loader?
// 答:var $ = require("expose-loader?$!jquery");希望把jquery暴露出去,暴露为"$",暴露给全局上
console.log(‘内联window.$,‘,window.$)

var path = require(‘path‘);
let HtmlWebpackPlugin = require(‘html-webpack-plugin‘)
let MiniCssExtractPlugin = require(‘mini-css-extract-plugin‘);
let OptimizeCssAssetsWebpackPlugin = require(‘optimize-css-assets-webpack-plugin‘);//压缩.css文件
let UglifyjsWebpackPlugin = require(‘uglifyjs-webpack-plugin‘);//压缩js
module.exports = {
    optimization:{//优化项
        minimizer:[
            new OptimizeCssAssetsWebpackPlugin(),
            new UglifyjsWebpackPlugin({
                cache:true,//启用缓存
                parallel:true,//并发打包
                sourceMap:true
            })
        ]
    },
    mode: "production",//模式:production/development
    entry: ‘./src/index.js‘,
    output: {
        filename: "bundle.[hash:6].js", // 可以指定打包后的文件名不同,bundle.[hash:6].js 可以指定hash的长度
        path: path.resolve(__dirname, ‘build‘),//路径必须是绝对路径
    },
    devServer: {
        //开发服务配置
        port: 3000,//端口
        progress: true,//显示进度
        contentBase: ‘./build‘, //静态服务运行目录
        compress: true,//压缩

    },
    plugins: [
        new HtmlWebpackPlugin({
            template: "./src/index.html",
            filename: "index.html",
            minify: {
                removeAttributeQuotes: true,//把index.html双引号转化为单引号
                collapseWhitespace: true,//折叠空行
            },
            hash: true,//文件添加hash戳,防止服务器环境缓存,比如apach或者nginx
        }),
        new MiniCssExtractPlugin({
            filename: ‘main.css‘,// 抽离出来的样式文件


        })
    ],//webpack插件
    module: {
        rules: [
            {
                test:/\.js$/,
                use:{
                    loader:‘babel-loader‘,
                    options:{
                        presets:[ // 预设
                            "@babel/preset-env"
                        ]
                    }
                }
            },
            {
                test: require.resolve(‘jquery‘),
                use:‘expose-loader?$‘
            },
            // 解析css,css-loader 主要负责解析@import.style-loader 把 css 插入到 head标签中
            // loader 用法: 字符串
            // 多个loader:数组，loader有顺序,从右向左执行
            // {
            //     test: /\.css$/, use: [{
            //         loader: ‘style-loader‘,
            //         options: {
            //             insert: function insertAtTop(element) {
            //                 var parent = document.querySelector(‘head‘);
            //                 // eslint-disable-next-line no-underscore-dangle
            //                 var lastInsertedElement =
            //                     window._lastElementInsertedByStyleLoader;

            //                 if (!lastInsertedElement) {
            //                     parent.insertBefore(element, parent.firstChild);
            //                 } else if (lastInsertedElement.nextSibling) {
            //                     parent.insertBefore(element, lastInsertedElement.nextSibling);
            //                 } else {
            //                     parent.appendChild(element);
            //                 }
            //                 // eslint-disable-next-line no-underscore-dangle
            //                 window._lastElementInsertedByStyleLoader = element;
            //             },
            //         }

            //     }, ‘css-loader‘]
            // },
            {
                test: /\.css$/, use: [
                    MiniCssExtractPlugin.loader, 
                    ‘css-loader‘,
                    ‘postcss-loader‘
                ]
            }
        ]
    }
}