<!DOCTYPE html>
<html>
<body>
<p>Click anywhere in the document (the right frame) to get focus. If you click outside the document, it will lose focus.</p>
<p id="demo"></p>
<script>
setInterval("myFunction()", 1);
function myFunction() {
var x = document.getElementById("demo");
if (document.hasFocus()) {
x.innerHTML = "The document has focus.";
} else {
x.innerHTML = "The document DOES NOT have focus.";
}
}
</script>
</body>
</html>