<!DOCTYPE html>
<html>
<body>
<p>Click "Try it". Wait 3 seconds. The page will alert "Hello".</p>
<p>Click "Stop" to prevent the first function to execute.</(p>
<p>(You must click "Stop" before the 3 seconds are up.)</p>
<button onclick="myVar = setTimeout(myFunction, 3000)">Try it</button>
<button onclick="clearTimeout(myVar)">Stop it</button>
<script>
function myFunction() {
alert("Hello");
}
</script>
</body>
</html>