check window innerwidth code example

Example 1: JS get viewport width

//getting the viewport dimensions
var width= Math.max(document.documentElement.clientWidth, window.innerWidth || 0);
var height = Math.max(document.documentElement.clientHeight, window.innerHeight || 0);

Example 2: get window height javascript

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

<script>
document.getElementById("demo").innerHTML = 
"Screen width is " + screen.width;
</script>