How to add a timer in HTML5 and Javascript?

I'm trying to to add a timer for a Snake Game and to start it simultaneously when the game starts and to stop it when it's finished. Any help please? Many thanks!

The example below (just sample code) it will count 5 secs and then alert the total seconds. You need to make the math to get hours, minutes, seconds.

$(document).ready(function(){
var secs = 0;
var id = setInterval(function(){ 
    secs++; console.log(secs);
  if(secs> 5){
    clearInterval(id);
    alert('Total Time: ' + secs + ' seconds');
   }
}, 1000);
});

Then you can put the logic inside a start/stop method or wherever you need to place it.

With pure Javascript:

window.onload = function() {
var secs = 0;
    var id = setInterval(function(){ 
        secs++; console.log(secs);
      if(secs> 5){
        clearInterval(id);
        alert('Total Time: ' + secs + ' seconds');
       }
    }, 1000);
};