Tryit Editor v2.7

Edit This Code:
<!DOCTYPE html>
<html>
<body>

<p>Click the button to display the available height of your screen.</p>

<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

<script>
function myFunction() {
    var x = "Available Height: " + screen.availHeight + "px";
    document.getElementById("demo").innerHTML = x;
}
</script>

</body>
</html>