JSFiddle - React, Tailwind, and code Playground

HTML

Time: <span id='Time'>

</span>
<br>

JavaScript

function waitHeadForIt() { //50<>100 ms
      var start = new Date();
      var xhttp = new XMLHttpRequest();
      xhttp.open("HEAD", "", false);
      xhttp.send();
      xhttp.abort();
      var end = new Date();
      return (end - start);
  }

  function waitLongForIt() { //500<>1000 ms
      var start = new Date();
      var xhttp = new XMLHttpRequest();
      xhttp.open("POST", "WaitForIt", false);
      xhttp.send();
      xhttp.abort();
      var end = new Date();
      return (end - start);
  }

  function waitForIt() { //200<>500 ms
      var start = new Date();
      var xhttp = new XMLHttpRequest();
      xhttp.open("GET", "WaitForIt", false);
      xhttp.send();
      var end = new Date();
      return (end - start);
  }
  //
  function waitIFShort() { //5<>10 ms
      var start = new Date();
      var ifram = document.createElement('iframe');
      ifram.id = 'ifram';
      ifram.src = window.location.href;
      var div = document.createElement('div');
      div.id = 'timer';
      document.body.appendChild(div);
      document.getElementById('timer').appendChild(ifram);
      document.getElementById('timer').removeChild(ifram);
      document.body.removeChild(div);
      var end = new Date();
      return (end - start);
  }



  function waitIF() { //100<>200 ms
      var start = new Date();
      var ifram = document.createElement('iframe');
      ifram.id = 'ifram';
      ifram.src = '';
      var div = document.createElement('div');
      div.id = 'timer';
      document.body.appendChild(div);
      document.getElementById('timer').appendChild(ifram);
      document.getElementById('timer').removeChild(ifram);
      document.body.removeChild(div);
      var end = new Date();
      return (end - start);
  }



  function waitD() { //0<>5 ms
      var start = new Date();
      var div = document.createElement('div');
      div.id = 'timer';
      document.body.appendChild(div);
      div.click();
      document.body.removeChild(div);
      var...