JSFiddle - React, Tailwind, and code Playground

JavaScript

$(document).ready(function () {
     
      $.ajax({
        type: 'POST',
        url:'http://localhost:8080/rest/test',
        dataType:'json',
				async:true,
        headers:{aaa:"abck"},
        data: '',
        complete: function(resp){
            alert(resp.getAllResponseHeaders());
             }});
        
    });