How to create pause function in timer?

Using "getTimer()" on timer update will not allow you to pause the timer properly, so you need to count the remaining time in another way:

var endTime:int = getTimer();

endTime += 40*60*1000;  //adjust endTime to 15 minutes in the future.

var countdownTimer:Timer = new Timer(1000);

countdownTimer.addEventListener(TimerEvent.TIMER, updateTime);

countdownTimer.start();

function updateTime(e:TimerEvent):void

{

    endTime -= 1000

    var timeLeft:Number = endTime;

  var seconds:Number = Math.floor(timeLeft / 1000);

  var minutes:Number = Math.floor(seconds / 60);

  seconds %= 60;

  minutes %= 60;

  var sec:String = seconds.toString();

  var min:String = minutes.toString();

  if (sec.length < 2) {

    sec = "0" + sec;

  }

  if (min.length < 2) {

    min = "0" + min;

  }

  var time:String = min + ":" + sec;

  countdown.text = time;

}

// this button will pause the timer using Boolean variable:

var pause:Boolean = false;

my_btn.addEventListener(MouseEvent.CLICK, onClick);

function onClick(e:MouseEvent):void

{

    if(pause == false)

    {

        countdownTimer.stop();

        pause = true;

    }

    else

    {

        countdownTimer.start();

        pause = false;

    }

}