Javascript Timer using Web Worker (Async Timer)

javascript_timer_web_worker_async_timer.js

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

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

/* ---- */

// script.js
var worker = new Worker('worker.js');
  
worker.addEventListener('message', function(e) {
  $('#timer').text(e.data);
});
  
worker.postMessage('run the timer');

function hangTheBrowser() {
  let val = "";

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

/* ---- */

// worker.js
self.addEventListener('message', function(e) {
  if(e.data === 'run the timer') {
    let count = 0;
    
    setInterval(_ => {
      count+=10;
  
      let ms = count % 1000;
      let s = Math.floor((count /  1000)) % 60;
      let m = Math.floor((count / 60000)) % 60;
  
      let time = m + ":" + s + ":" + ms;
      
      self.postMessage(time);
    }, 10);
  }
});