JSFiddle - React, Tailwind, and code Playground

HTML

<p id='demo'>

</p>

JavaScript

function waitForIt(){
 var start=new Date();
 var xhttp = new XMLHttpRequest();
  xhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
      document.getElementById("demo").innerHTML =
      this.responseText;
    }
  };
  xhttp.open("GET", "WaitForIt", false);
  xhttp.send();
  var end=new Date();
  }
  function wait(time){
  var start=new Date();
  var end=new Date();
  while((end-start<time)){
  waitForIt();
  end=new Date();
  }
  return (end - start);
  }
  
  
  function sleeps(){
  var start=new Date();
  var ifram = document.createElement('iframe');
  ifram.src='';
  document.appendChild(ifram);
   var end=new Date();
   return (end - start);
  }
  
  document.getElementById("demo").innerHTML=sleeps();