1.安装express

npm i express-generator
express app -e
cd app
npm i

2.目录分析

node_modules：依赖的模块包
public：存放静态资源
routes：路由操作
views：存放ejs模板引擎
app.js：主文件
package.json：项目描述文件
node www运行   
默认端口3000

3.创建监听端口

app.js
var http = require("http");
//server 要在app下
var server = http.createServer(app);
server.listen(5000, () => {
  console.log("启动成功,端口号5000");
});

4.新建config文件夹

configdb.js
npm  i mysql 
var mysql = require("mysql");
var pool = mysql.createPool({
  connectionLimit: 20,
  host: "127.0.0.1",
  user: "root",
  password: "root",
  database: "wit.mes",
  port: 3306,
});
module.exports = pool;

5.routes文件夹

var express = require("express");
var router = express.Router();
var pool = require("../config/configdb");
//get
router.get("", (req, res, next) => {
  pool.getConnection((err, conn) => {
    if (err) {
      console.log(err);
    } else {
      console.log(req.query);
      var sql = ``;
      conn.query(sql, (err, data) => {
        if (err) {
          console.log(err);
        } else {
          res.send({
            code: "0000",
            data,
          });
          conn.release();
        }
      });
    }
  });
});
//post
router.post("", (req, res, next) => {
  pool.getConnection((err, conn) => {
    if (err) {
      console.log(err);
    } else {
      var sql = ``;
      conn.query(sql, (err, data) => {
        if (err) {
          console.log(err);
        } else {
          console.log("ok");
          res.send({
            code: "0000",
            data: "ok",
          });
          conn.release();
        }
      });
    }
  });
});

6.app.js中引入

var indexRouter = require('./routes/index');
...

//404上面use 
app.use('/', indexRouter);

7.package.json

npm i nodemon 
"scripts": {
    "start": "node app.js",
    "server": "nodemon server.js"
  },

8.启动

npm run server