onclick timer javascript

1//single event i.e. alarm, time in milliseconds
2var timeout = setTimeout(function(){yourFunction()},10000);
3//repeated events, gap in milliseconds
4var interval = setInterval(function(){yourFunction()},1000);

1document.getElementById("gameStart").addEventListener("click", function(){
2    var timeleft = 15;
3
4    var downloadTimer = setInterval(function function1(){
5    document.getElementById("countdown").innerHTML = timeleft + 
6    " "+"seconds remaining";
7
8    timeleft -= 1;
9    if(timeleft <= 0){
10        clearInterval(downloadTimer);
11        document.getElementById("countdown").innerHTML = "Time is up!"
12    }
13    }, 1000);
14
15    console.log(countdown);
16});