Javascript Timer using Date method

javascript_timer_date.js

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

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

// script.js
let start = new Date();
let intervalRef = null;

intervalRef = setInterval(_ => {
  let current = new Date();
  let count = +current - +start;
  
  let ms = count % 1000;
  let s = Math.floor((count /  1000)) % 60;
  let m = Math.floor((count / 60000)) % 60;

  $('#timer').text(m + ":" + s + ":" + ms);
}, 10);

function hangTheBrowser() {
  let val = "";

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