JSFiddle - React, Tailwind, and code Playground

HTML

<button>test1</button>
<button>test2</button>
<button>test3</button>
<button>test4</button>
<button>test5</button>

JavaScript

var reqs = [];
Array.prototype.forEach.call(document.querySelectorAll("button"),function(btn)
                             {
                                 btn.onclick = function()
                                 {
                                     var index = reqs.length;
                                     reqs[index] = false;
                                     function reqListener () {
                                         //console.log(this.responseText);
                                         reqs[index] = true;
                                         var allFinished = true;
                                         reqs.forEach(function(req)
                                                      {
                                                          if(!req)
                                                          {
                                                              allFinished = false;
                                                          }
                                                      });
                                         if(allFinished)
                                         {
                                             alert("finished!!!!!!!!");
                                         }
                                     }
                                     
                                     var request = new XMLHttpRequest();
                                     request.onload = reqListener;
                                     request.open("get", "http://fiddle.jshell.net/", true);
                                     request.send();
                                 };
                             });