1const window {
2  width: window.innerWidth,
3  height: window.innerHeight
4}

1// better than using window.innerWidth / window.innerHeight 
2// because of scrollbars
3const client = {
4      width: document.documentElement.clientWidth,
5      height: document.documentElement.clientHeight
6}

1<p id="demo"></p>
2
3<script>
4document.getElementById("demo").innerHTML = 
5"Screen width is " + screen.width;
6</script>