在没有用devServer之前我们都是打包之后，通过文件的方式运行index.html文件,并且每改变一次代码都要重新打包,这样不仅不可以发送ajax请求而且会使得我们的开发效率极其低下.
那么我们可以通过devserver在本地运行一个node环境,通过http的形式访问index.html文件并保持实时更新.

watch

在package.json中配置 "serve":"webpack --watch"

//完整代码:
{
  "name": "webpack-demo",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "serve":"webpack --watch"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "clean-webpack-plugin": "^3.0.0",
    "css-loader": "^3.1.0",
    "file-loader": "^4.1.0",
    "html-webpack-plugin": "^3.2.0",
    "node-sass": "^4.12.0",
    "sass-loader": "^7.1.0",
    "style-loader": "^0.23.1",
    "webpack": "^4.37.0",
    "webpack-cli": "^3.3.6"
  }
}

通过这种方式可以实现不用重复打包,但打包的项目还是以文件的形式运行不可以发送ajax请求.不推荐使用

devServer

配置webpack.config.js中添加

devServer:{
    contentBase:'./dist',
    open:true，
    port:8000
}

const path=require('path');
const HtmlWebpackPlugin=require('html-webpack-plugin');
const {CleanWebpackPlugin}= require('clean-webpack-plugin');
module.exports={
    mode:'development',
    devtool:'source-map',
    entry:{
        main:'./index.js'
    },
    devServer:{
        contentBase:'./dist',
        open:true,
        port:8080
    },
    module:{
        rules:[
            {
                test:/\.jpg$/,
                use:{
                    loader:'file-loader',
                    options:{
                        outputPath:'images',
                        name:'img.jpg'
                    }
                }
            },
            {
                test: /\.css$/,
                use: ['style-loader', 'css-loader'],
            },{
                test: /\.scss$/,
                use: [
                    "style-loader", // creates style nodes from JS strings
                    "css-loader", // translates CSS into CommonJS
                    "sass-loader" // compiles Sass to CSS, using Node Sass by default
                ]
            }
        ]
    },
    output:{
        path:path.resolve(__dirname,'./dist'),
        filename:'index_bundle.js'
    },
    plugins:[new HtmlWebpackPlugin({
        template:'./index.html'
    }),new CleanWebpackPlugin()]
}

配置package.json

"start":"webpack-dev-server"

{
  "name": "webpack-demo",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "serve":"webpack --watch",
    "start":"webpack-dev-server"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "clean-webpack-plugin": "^3.0.0",
    "css-loader": "^3.1.0",
    "file-loader": "^4.1.0",
    "html-webpack-plugin": "^3.2.0",
    "node-sass": "^4.12.0",
    "sass-loader": "^7.1.0",
    "style-loader": "^0.23.1",
    "webpack": "^4.37.0",
    "webpack-cli": "^3.3.6"
  }
}

安装webpack-dev-server

npm install webpack-dev-server

运行:npm run start即可.