1.将打包后的css与js分割开

安装mini-css-extract-plugin,并使用这个插件
npm i mini-css-extract-plugin

const {resolve}=require('path')
const HtmlWebpackPlugin = require("html-webpack-plugin");
const MiniCssExtractPlugin=require('mini-css-extract-plugin')
module.exports={
    entry:'./src/js/index.js',
    output:{
        filename:'js/bundle.js',
        path: resolve(__dirname,'dist')
    },
    module:{
        rules:[
            {
                test: /\.css$/,
                use: [
                //   "style-loader",
                //这个loader取代style-loader可以将css分隔开
                MiniCssExtractPlugin.loader,
                  //将css转化为js
                  "css-loader",
                ],
            }
        ]
    },
    plugins:[
        new  HtmlWebpackPlugin({
            template:'./src/index.html'
        }),
       new MiniCssExtractPlugin({
           //对打包后css重命名，并将之放入一个文件
           filename:'css/built.css'
       })
    ],
    mode:'development'
}

2.解决css兼容性问题

下载两个包postcss-loader postcss-preset-env
npm i postcss-loader postcss-preset-env

//package.json
"browserslist": {
    "development": [
      "last 1 chrome version",
      "last 1 firefox version",
      "last 1 safari version"
    ],
    "production": [
      ">0.2%",
      "not dead",
      "not op_mini all"
    ]
  }

//webpack.config.js
const { resolve } = require("path");
const HtmlWebpackPlugin = require("html-webpack-plugin");
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
//设置node环境变量，默认是生产环境production
process.env.NODE_ENV = "development";
module.exports = {
  entry: "./src/js/index.js",
  output: {
    filename: "js/bundle.js",
    path: resolve(__dirname, "dist"),
  },
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          MiniCssExtractPlugin.loader,
          //将css转化为js
          "css-loader",
          //使用postcss-loader
          {
            loader: "postcss-loader",
            options: {
              postcssOptions: {
                ident: "postcss",
                plugins: () => [
                  //帮助css找到package.json中的browserslist里面的配置，通过加载指定的css样式
                  require("postcss-preset-env")(),
                ],
              },
            },
          },
        ],
      },
    ],
  },
  plugins: [
    new HtmlWebpackPlugin({
      template: "./src/index.html",
    }),
    new MiniCssExtractPlugin({
      //对打包后css重命名，并将之放入一个文件
      filename: "css/built.css",
    }),
  ],
  mode: "development",
};

3.压缩css

下载 optimize-css-assets-webpack-plugin

npm  i optimize-css-assets-webpack-plugin -D

使用

const OptimizeCssAssetsWebpackPlugin=require("optimize-css-assets-webpack-plugin")
plugins: [
    new OptimizeCssAssetsWebpackPlugin()
  ],