<html>
<body>
<p>Click the first button alert "Hello" after waiting 3 seconds.</p>
<p>Click the second button to prevent the first function to execute. (You must click it before the 3 seconds are up.)</p>
<button onclick="myFunction()">Try it</button>
<button onclick="myStopFunction()">Stop the alert</button>
<script>
var myVar;
function myFunction()
{
myVar=setTimeout(function(){alert("Hello")},3000);
}
function myStopFunction()
{
clearTimeout(myVar);
}
</script>
</body>
</html>