第一步；entry: [

"webpack-dev-server/client?http://localhost:8080/",

"webpack/hot/only-dev-server",

"./app"

],

第二步：

plugins: [

new webpack.HotModuleReplacementPlugin(),

}

第三步： "start": "webpack-dev-server --inline --hot --quiet"

第四步："devDependencies": {? "webpack-dev-server": "^1.16.1",}