get window size javascript

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

<script>
document.getElementById("demo").innerHTML = 
"Screen width is " + screen.width;
</script>const window {
  width: window.innerWidth,
  height: window.innerHeight
}var win = window,
    doc = document,
    docElem = doc.documentElement,
    body = doc.getElementsByTagName('body')[0],
    x = win.innerWidth || docElem.clientWidth || body.clientWidth,
    y = win.innerHeight|| docElem.clientHeight|| body.clientHeight;
alert(x + ' × ' + y);