npm install webpack-dev-server -g 

npm install webpack-dev-server --save-dev

  module.exports = {
            entry:"./js/index.js",
            output:{
                path:"/",     
 //注意这里的改变，必须是根目录,指定目录无效，因为webpack会在内存中根目录下生成下面文件名。
                filename:"bundle.js"
            },
            module:{
                loaders:[
                    { test:/\.css$/,loader:'style-loader'},
                    { test:/\.css$/,loader:'css-loader'}
                ]
            },
            resolve:{
                extensions:['.vue','.js',".css",'jsx'] //自动补全识别后缀
            }
    }

<script type="text/javascript" src="bundle.js"></script>

webpack-dev-server --hot --inline