get window resolution javascript

1var clientWidth = document.documentElement.clientWidth;
2 $("h2").text(clientWidth);

1alert("Your screen resolution is: " + screen.width + "x" + screen.height)

1var win = window,
2    doc = document,
3    docElem = doc.documentElement,
4    body = doc.getElementsByTagName('body')[0],
5    x = win.innerWidth || docElem.clientWidth || body.clientWidth,
6    y = win.innerHeight|| docElem.clientHeight|| body.clientHeight;
7alert(x + ' × ' + y);