Simple use of express web server

//  introduce express
const express=require("express");
//  Create a express The server 
const app=express();
// Set the path and method of the request , Execute the callback function after the request succeeds 
app.get('/server',(request,response)=>{
    //  Set the response header , To solve the cross domain 
    response.setHeader('Access-Control-Allow-Origin','*')

    //  Set the response body 
    response.send("hhhh")
})

//  Start the service  
app.listen(9000,()=>{
    console.log(" The server has started , port 9000 Monitoring ....")
})

Sending AJAX When setting url Parameter method

app.get('/server',(request,response)=>{})   
// Set parameters in the address bar 
// stay server Pass it with a question mark later     Multiple parameters with & separate 

in the light of AJAX Sending requests will cause cache problems

We put a timestamp after the requested path for example '127.0.0.1:8080/server?t='+Data.now()

About AJAX request timeout , We need to set a timeout on the front end

// The timeout is set to 2s, Is if you ask 2s Not yet requested , Just cancel the request 
xhr.timeout=2000
// We can also set a callback for request timeout 
xhr.ontimeout=function(){}
// Callback of network exception 
xhr.οnerrοr=function(){}