webpack-dev-middleware 作用

webpack-dev-middleware 作用：
在启动node后端服务时自动启动webpack打包相关程序
安装：

npm安装：
npm install webpack-dev-middleware --save-dev
yarn安装：
yarn add webpack-dev-middleware --dev

例子：

app.js:

const webpack = require('webpack');
const middleware = require('webpack-dev-middleware');
const config = require('./webpack.config.js');
//参数引入配置好的webpack.config.js文件
const compiler = webpack(config);
const express = require('express');
const app = express();

app.use(middleware(compiler));

//下面是请求接口
app.get('/user', (req, res) => {
	res.send({name:'我是user接口的数据'})
})

app.listen(3000, () => console.log('Example app listening on port 3000!'));

配置好后node启动app.js即可自动启动配置好的webpack.config.js打包文件：

node app.js