A brief discussion on the types of node.js middleware

const express = require('express');
var server = express();
server.listen(3000);
//Middleware interception registration route/reg
server.use('/reg',(req,res,next)=>{
    console.log('Registration verification');
    next();
});

server.use('/login',(req,res)=>{
    console.log('Log recorded');
})
server.get('/reg',(req,res,next)=>{
    res.send('Registration successful');
    next();
});

server.get('/login',(req,res)=>{
    res.send('Login successful');
})

server.use(express.static('目录'))

const express = require('express');
//Introduce body-parser middleware const bodyParser=require('body-parser');

var server = express();
server.listen(3000);
// Host static resources to public
server.use(express.static('./public'));

//Use body-parser middleware to parse the post request data into an object //Extended Whether to use the extended qs module to parse into an object //If false, do not use it, and use the querystring module instead server.use(bodyParser.urlencoded(
    {extended:false}
))

server.post('/mylogin',(req,res)=>{
    console.log(req.body);
    res.send('Login successful');
})

//Introduce the mysql module const mysql =require('mysql');
//1. Normal connection //1.1 Create a connection var connection = mysql.createConnection({
    host:'127.0.0.1',
    port:'3306',
    user:'root',
    password:'1234',
    database:'tedu'
});
//1.2 Execute connection connection.connect();
//Execute SQL statement connection.query('select * from emp',(err,result)=>{
    if(err) throw err;
    console.log(result);
});
//Close the connectionconnection.end();

const mysql = require('mysql');
//Use connection pool //Create connection pool object var pool = mysql.createPool(
    {
        host:'127.0.0.1',
        port:'3306',
        user:'root',
        password:'1234',
        database:'tedu',
        connectionLimit:20
    }
);
//Execute SQL statement pool.query('select * from emp where eid=2',(err,result)=>{
    if(err) throw err;
    console.log(result);
})
const mysql = require('mysql');
var pool = mysql.createPool({
    'host':'127.0.0.1',
    port:'3306',
    user:'root',
    password:'1234',
    database:'tedu',
    connectionLimit:20
})
//Use placeholders to insert data // pool.query("insert into emp values(?,?,?,?,?,?)",[null,'yt','1','1995-12-24','9000','20'],(err,result)=>{
// if(err) throw err;
// console.log(result);
// });
//Use object to insert data//var emp={
// eid:null,
// ename:'html',
// sex:1,
// birthday:'1995-12-25',
//salary:10000,
//deptid:30
// }
// pool.query('insert into emp set ?',[emp],(err,result)=>{
// if(err) throw err;
// console.log(result);
// })
//Use the placeholder to delete the data numbered 10 pool.query('delete from emp where eid=?',[10],(err,result)=>{
    if(err) throw err;
    console.log(result);
    if(result.affectedRows>0){
        console.log('Deleted successfully');
    }
    else{
        console.log('deletion failed');
    }
})