var timerID = '';
var pocetSekund = 0;
/**
 * initTimer
 * @param {int} secs 
 */
 function initTimer(secs) {
 	var timerDiv = document.getElementById('timer');
 	if (timerDiv != null) {
	 	var s = Math.round(secs%60);
	 	var m = Math.floor(secs/60);
	 	timerDiv.innerHTML = (m < 10 ? '0'+m : m) + ':' + (s < 10 ? '0'+s : s);
	 	timerID = window.setInterval('doTimerStep()', 1000);
	 	pocetSekund = secs;
 	}
 }

 function doTimerStep() {
 	var timerDiv = document.getElementById('timer');
 	var arr = timerDiv.innerHTML.split(':');
 	var min = parseInt(arr[0],10);
 	var sec = parseInt(arr[1],10);
// 	new Number
 	
 	--sec;
 	if (sec < 0) {
 		--min;
 		if (min < 0) {
 			window.clearInterval(timerID);
 			return;
 		} else {
 			sec = 59;
 		}
 	}
 	
 	min = min < 10 ? '0'+min:min;
 	sec = sec < 10 ? '0'+sec:sec;
 	
 	if (min < 1) {
 		timerDiv.style.color = 'red';
 		timerDiv.style.fontWeight = 'bold';
 	} 
 	
 	timerDiv.innerHTML = min+':'+sec;
 }
 
 function resetTimer(){
	 var timerDiv = document.getElementById('timer');
	 if (timerDiv != null) {
		 var s = Math.round(pocetSekund%60);
		 var m = Math.floor(pocetSekund/60);
		 timerDiv.innerHTML = (m < 10 ? '0'+m : m) + ':' + (s < 10 ? '0'+s : s);
	 }
 }