[JavaScript] Simpel countdown met verzenden formulier

<script type="text/javascript">
function CountDown() {
	var duration = Math.round(document.getElementById('display').innerHTML);
	var form = document.getElementById("myForm");
	if (isNaN(duration)) {
		return;
	} else {
		duration = duration + 1;
	}
	var InterVal = setInterval(nextSecond, 1000);
	function nextSecond(){
		duration--;
		if (duration < 0){
			clearInterval(nextSecond);
			document.getElementById('display').innerHTML = duration;
			form.submit();
		} else {
			document.getElementById('display').innerHTML = duration;
		}
	}
}
CountDown();
</script>