Untitled

<!DOCTYPE html>
<html>
<body>
<button onclick="myFunction()">show the window size</button>
<p id="demo"></p>
<script>
function myFunction() {
    var w = window.innerWidth;
    var h = window.innerHeight;
    document.getElementById("demo").innerHTML = "Width: " + w + "<br>Height: " + h;
}
</script>
</body>
</html>