I have javascript of stopwatch i want to start stop with oracle apex button. i create button and create dynamic action with Execute Javascript expression and paste javasctipt but it doesn't run.

var x;

var startstop = 0;



function startStop() { /* Toggle StartStop */



  startstop = startstop + 1;



  if (startstop === 1) {

    start();

    document.getElementById(start).innerHTML = Stop;

  } else if (startstop === 2) {

    document.getElementById(start).innerHTML = Start;

    startstop = 0;

    stop();

  }



}





function start() {

  x = setInterval(timer, 10);

} /* Start */



function stop() {

  clearInterval(x);

} /* Stop */



var milisec = 0;

var sec = 0; /* holds incrementing value */

var min = 0;

var hour = 0;



/* Contains and outputs returned value of  function checkTime */



var miliSecOut = 0;

var secOut = 0;

var minOut = 0;

var hourOut = 0;



/* Output variable End */





function timer() {

  /* Main Timer */





  miliSecOut = checkTime(milisec);

  secOut = checkTime(sec);

  minOut = checkTime(min);

  hourOut = checkTime(hour);



  milisec = ++milisec;



  if (milisec === 100) {

    milisec = 0;

    sec = ++sec;

  }



  if (sec == 60) {

    min = ++min;

    sec = 0;

  }



  if (min == 60) {

    min = 0;

    hour = ++hour;



  }





  document.getElementById(milisec).innerHTML = miliSecOut;

  document.getElementById(sec).innerHTML = secOut;

  document.getElementById(min).innerHTML = minOut;

  document.getElementById(hour).innerHTML = hourOut;



}





/* Adds 0 when value is <10 */





function checkTime(i) {

  if (i < 10) {

    i = 0 + i;

  }

  return i;

}



function reset() {





  /*Reset*/



  milisec = 0;

  sec = 0;

  min = 0

  hour = 0;



  document.getElementById(milisec).innerHTML = 00;

  document.getElementById(sec).innerHTML = 00;

  document.getElementById(min).innerHTML = 00;

  document.getElementById(hour).innerHTML = 00;



}

this is html code. this heading i added into static content. I think this fucntion need to call in button of oracle apex onclick=startStop()

<h1>

  <span id=hour>00</span> :

  <span id=min>00</span> :

  <span id=sec>00</span> :

  <span id=milisec>00</span>

</h1>



<button onclick=startStop() id=start>Start</button>

<button onclick=reset()>Reset</button>