var sec = 0;
var min = 0;
function stopwatch() {
      sec++;
      if (sec == 60) {
         sec = 0;
         min += 1;
      }
      totalTime = ((min<=9) ? "0" + min : min) + " : " + ((sec<=9) ? "0" + sec : sec);
      document.getElementById("timer").innerHTML = totalTime;
      start = setTimeout("stopwatch()", 1000);
   }