JavaScript Viewport – How to Get Browser Viewport Dimensions

You might try this:

function getViewport() {

 var viewPortWidth;
 var viewPortHeight;

 // the more standards compliant browsers (mozilla/netscape/opera/IE7) use window.innerWidth and window.innerHeight
 if (typeof window.innerWidth != 'undefined') {
   viewPortWidth = window.innerWidth,
   viewPortHeight = window.innerHeight
 }

// IE6 in standards compliant mode (i.e. with a valid doctype as the first line in the document)
 else if (typeof document.documentElement != 'undefined'
 && typeof document.documentElement.clientWidth !=
 'undefined' && document.documentElement.clientWidth != 0) {
    viewPortWidth = document.documentElement.clientWidth,
    viewPortHeight = document.documentElement.clientHeight
 }

 // older versions of IE
 else {
   viewPortWidth = document.getElementsByTagName('body')[0].clientWidth,
   viewPortHeight = document.getElementsByTagName('body')[0].clientHeight
 }
 return [viewPortWidth, viewPortHeight];
}

( http://andylangton.co.uk/articles/javascript/get-viewport-size-javascript/ )

However, it is not even possible to get the viewport information in all browsers (e.g. IE6 in quirks mode). But the above script should do a good job :-)

These days, for screen size you can use the screen object:

window.screen.height;
window.screen.width;

Legacy

You can get the size of the window or document with jQuery:

// Size of browser viewport.
$(window).height();
$(window).width();

// Size of HTML document (same as pageHeight/pageWidth in screenshot).
$(document).height();
$(document).width();