Obtain screen/window/document dimensions

dimension.js

/**
 * Obtain screen/window/document(.documentElement)/element dimensions
 * @param  object target
 * @param  mixed  prefix  [optional, default false-ish - no prefix, use best for target]
 * @note   best:
 *         - window   >> outer
 *         - document >> client|offset|scroll
 *         - element  >> client|offset|scroll
 */
function dimension(target, prefix) {
	var prop = function(name, fix) {
			return (!(fix && fix.length) ? [name] : [].concat(fix))
				.map(function(p) {
					return (target ? target[p && fix ? p + name[0].toUpperCase() + name.substr(1) : name] : null) || 0;
				});
		};

	target = target === document ? document.documentElement : target;
	prefix = prefix || (target && 'nodeType' in target ? ['client', 'offset', 'scroll'] : (target === window ? 'outer' : null));

	return [
		Math.max.apply(Math, prop('width', prefix)),
		Math.max.apply(Math, prop('height', prefix))
	].join('/');
}

usage.js

dimension(screen);           //  <width>/<height>
dimension(screen, 'avail');  //  <availWidth>/<availHeight>
dimension(window);           //  <outerWidth>/<outerHeight>
dimension(window, 'inner');  //  <innerWidth>/<innerHeight>
dimension(document);         //  <max clientWidth|offsetWidth|scrollWidth>/<max clientHeight|offsetHeight|scrollHeight>
                             //  document as target will actually use document.documentElement