npm i webpack-dev-server

"dev":"WebPack-dev-server --config webpack.config.js” 

target:"web" 

npm i cross-env

"build": "cross-env NODE_ENV=production webpack --config webpack.config.js",
"dev": "cross-env NODE_ENV=development webpack-dev-server --config webpack.config.js"

const isDev = process.env.NODE_ENV ==='development' 

module.exports = config

if（isDev）{
 config.devtool =“＃廉价模块-EVAL-源映射”//代码映射
 config.devServer = {
  port:8000,//启动服务监听端口
  host:'0.0.0.0'，//可以通过localhost访问
  overlay:{//在页面上显示错误信息
   errors：true，
   },
   open:true，//启动webpack-dev-server时自动打开浏览器
   hot:true //启用热更
 } 
 config.plugins.push(
  new webpack.HotModuleReplacementPlugin()，
  new webpack.NoEmitOnErrorsPlugin()//热更相关插件
 )
} 

npm i html-webpack-plugin

const HTMLPlugin = require('html-webpack-plugin')

 plugins: [
    new webpack.DefinePlugin({
      'process.env': {
        NODE_ENV: isDev "development"' : '"production"'
      }
    }),
    new HTMLPlugin()
  ]

npm run dev