Javascript Timer using Request Animation Frame

javascript_timer_request_animation_frame.js

// index.html
<p id="timer">
  00:00:00
</p>

<button onClick="hangTheBrowser()">
  Hang the browser
</button>

// script.js
let count = 0;
let rAF_ID;

var rAFCallback = function(callback) {
  let count = callback;

  let ms = Math.floor(count % 1000);
  let s = Math.floor((count /  1000)) % 60;
  let m = Math.floor((count / 60000)) % 60;

  $('#timer').text(m + ":" + s + ":" + ms);
  rAF_ID = requestAnimationFrame( rAFCallback );
}

// request animation frame on render
rAF_ID = requestAnimationFrame( rAFCallback );  

function hangTheBrowser() {
  let val = "";

    for(let i=0; i<10000; i++){
      for(let j=0; j<10000; j++) {
        val = "Loop returned: " + i + j;
      }
    }
}