JavaScript Infinite Timer

<html>
<head>
<script type="text/javascript"/>
var c=0;
var t;
var timer_is_on=0;

function timedCount()
{
document.getElementById('txt').value=c;
c=c+1;
t=setTimeout("timedCount()",500);
}

function doTimer()
{
if (!timer_is_on)
  {
  timer_is_on=1;
  timedCount();
  }
}
</script>
</head>
<body>
<form>
<input type="button" value="Start count!" onClick="doTimer()" />
<input type="text" id="txt" />
</form>
By clicking on the button the input field will count forever, starting at 0.
</body>
</html>

Demonstration Video[]

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