CORS Introduce

CORS It's a W3C standard , The full name is " Cross-domain resource sharing "（Cross-origin resource sharing）.

It allows the browser to cross to the source server , issue XMLHttpRequest request , To overcome AJAX A restriction that can only be used with the same origin .

CORS Requires both browser and server support . at present , All browsers support this feature ,IE The browser cannot be lower than IE10.

Whole CORS Communication process , It's all done automatically by the browser , No user involvement is required . For developers ,CORS Correspondence and homology AJAX There is no difference in communication , The code is exactly the same . Once the browser finds AJAX Request cross source , Will automatically add some additional header information , Sometimes there is an additional request , But users don't feel .

therefore , Realization CORS The key to communication is the server . As long as the server implements it CORS Interface , You can communicate across sources .

NodeJS Realization CORS Cross domain

stay phpnow In the environment （phpnow Default port 80） towards node( port 3000) Send a request

phpnow Request code in   （index.html）

     <script>
        $("button").click(function () {
            $.ajax({
                "url":'http://127.0.0.1:3000',
                "success": function(data){
                console.log(data,'data')
                }
            })
        })
    </script>

NodeJS The code in   app.js

var express = require("express")
var app = express()
app.get("/",function (req,res) { 
    // Configure the requested domain name ,* For any 
    res.header("Access-Control-Allow-Origin", "*");   
    //  Support cross domain request types 
    res.header("Access-Control-Allow-Methods","PUT,POST,GET,DELETE,OPTIONS");  
    // Configure request header information , Including character set, etc  
    res.header("Content-Type", "application/json;charset=utf-8");
    res.json({
        a:100
    })
})
app.listen(3000,function () {
    console.log(" monitor 3000")
})