Ajax1.0

const http=require('http');

let httpServer=http.createServer((req,res)=>{
res.setHeader('Access-Control-Allow-Origin','*');
res.write('aaaa');
res.end();
});

httpServer.listen(8080);

Ajax2.0

const http=require('http');
let allowHosts=['taobao.com','baidu.com'];
let httpServer=http.createServer((req,res)=>{
if(allowHosts.indexOf(req.headers['origin'])!=-1){
res.setHeader('Access-Control-Allow-Origin','*');
}
res.write('aaaa');
res.end();
});

httpServer.listen(8080);