Using nodejs as background request ajax failed

  node.js, question
//server
 const express = require('express');
 const app = express();
 
 
 
 app.use(express.static(__dirname));
 
 app.listen(8000);
 console.log('server running');
<!  DOCTYPE html>
 <html lang="en">
 <head>
 <meta charset="UTF-8">
 <title>Document</title>
 <script src="js/jquery-1.11.0.min.js"></script>
 </head>
 <body>
 <script>
 $.ajax({
 url: '/json/example.json',
 type: 'GET',
 dataType: 'json',
 
 })
 .done(function() {
 console.log("success");
 })
 .fail(function() {
 console.log("error");
 })
 .always(function() {
 console.log("complete");
 });
 
 </script>
 </body>
 </html>

Show the callback of fail, how to solve it?

There is no route in the background