Lap time

I am having difficulty to lap/split time in my Stopwatch. I have given it a try and it doesn't work. I am trying to get the event listener to fire for my Lap button. Can anyone help me out? If you need more code let me know because I am just providing a portion of it for this question. I have this due really soon. Thanks in advance!

var laps = 1;
 
var _startStopwatch = function() {
    timerlabel.value = '00:00:00.0';
 
var startTime = new Date();
var stopTime = startTime;
 
var _updateTimer = function updateTimer() {
    var UNIT_HOUR = 60 * 60 * 1000;
    var UNIT_MINUTE = 60 * 1000;
    var UNIT_SEC = 1000;
    var now = new Date();
    var diff = now.getTime() - startTime.getTime();
    var hour = Math.floor(diff / UNIT_HOUR);
    var minute = Math.floor((diff - hour * UNIT_HOUR) / UNIT_MINUTE);
    var sec = Math.floor((diff - hour * UNIT_HOUR - minute * UNIT_MINUTE) / UNIT_SEC);
    var msec = Math.floor(diff % UNIT_SEC);
    timerlabel.text = ('0' + hour).slice(-2) + ':' + ('0' + minute).slice(-2) + ':' + ('0' + sec).slice(-2) + '.' + ('00' + msec).slice(-1);
    };
    intervalid = setInterval(_updateTimer, 1000);
};
 
var _stopStopwatch = function() {
    clearInterval(intervalid);
}
 
var _resumeStopwatch = function(){
    clearInterval(intervalid);
    var startTime = new Date();
}
 
var started = false;
var intervalid = null;
var totaltime = 0;
var startTime = new Date();
var now = new Date();
var diff = now.getTime() - startTime.getTime();
var stopwatch;
 
//LAP FUNCTION
var _marklap = function(){
  if(started == 1)
   {
   if(lapdate != '')
    {
    var lapcounter = 0;
    var lapdate = '';
    var lapdetails;
    var lapold = lapdate.split(':');
    var lapnow = stopwatch.value.split(':');
    var lapcount = new Array();
    var x = 0
    for(x;x<lapold.length;x++)
     {
     lapcount[x] = new Array();
     lapcount[x][0] = lapold[x]*1;
     lapcount[x][1] = lapnow[x]*1;
     }
    if(lapcount[1][1] < lapcount[1][0])
     {
     lapcount[1][1] += 60;
     lapcount[0][1] -= 1;
     }
    if(lapcount[2][1] < lapcount[2][0])
     {
     lapcount[2][1] += 10;
     lapcount[1][1] -= 1;
     }
    var mzeros = (lapcount[0][1] - lapcount[0][0]) < 10?'0':'';
    var szeros = (lapcount[1][1] - lapcount[1][0]) < 10?'0':'';
    lapdetails.value += '\t+' + mzeros + (lapcount[0][1] - lapcount[0][0]) + ':' + szeros + (lapcount[1][1] - lapcount[1][0]) + ':' + (lapcount[2][1] - lapcount[2][0]) + '\n';
    }
   lapdate = stopwatch.value;
   lapdetails.value += (++lapcounter) + '. ' + stopwatch.value;
   }
  }
 
//LAP BUTTON
button04.addEventListener("click", function(e) {
    if(started){
        _marklap();
    }
});