Javascript/タイマー

var startBTn = document.getElementById("startBtn");
var time = document.getElementById("time");

function startTime(){
  startBtn.disabled = true;
  var waitTime = 3;
  var waitSecond = 3 * 60;
  
  var countTime = function(){
  	if(waitSecond > 0){
  	  waitSecond--;
  	  if(waitSecond > 60){
	  	if(waitSecond % 60 == 0){
	  	  waitTime--;
	  	}
	  blink(time);
	  time.innerHTML = waitTime;
	  } else {
	  	time.style.color = "black";
	  	time.innerHTML = waitSecond;
	  }
  	} else {
  	  timerStop();
  	}
  }
  var startCount = setInterval(countTime, 1000);
}

function timerStop(){
  startBtn.disabled = false;
  clearInterval(startCount);
}

function blink(element){
  if(element.style.color == "black"){
  	element.style.color = "gray";
  } else {
  	element.style.color = "black";
  }
}