Javascript function to return device type

Here’s a simple JS function to return the type of device based on screen size and some other helpful variables for the main manufacturers.

// mobile check
function checkForMobile() {

	var x = screen.width;
	var y = screen.height;
	var agent = navigator.userAgent.toLowerCase();
	var mobileOS = typeof orientation != 'undefined' ? true : false;
	var touchOS = ('ontouchstart' in document.documentElement) ? true : false;
	var otherBrowser = (agent.indexOf("series60") != -1) || (agent.indexOf("symbian") != -1) || (agent.indexOf("windows ce") != -1) || (agent.indexOf("blackberry") != -1);
	var iOS = (navigator.platform.indexOf("iPhone") != -1) || (navigator.platform.indexOf("iPad") != -1) ? true : false;
	var android = (agent.indexOf("android") != -1) || (!iOS && !otherBrowser && touchOS && mobileOS) ? true : false;
	var istablet = (/ipad|android|android 3.0|xoom|sch-i800|playbook|tablet|kindle/i.test(navigator.userAgent.toLowerCase()));
	var tablet = (istablet==true && x >= 768) ? true : false;

	// is it mobile

	if(x >= 320) {
		whichDevice = "Mobile";
	}

	if(tablet==true) {

		whichDevice = "Tablet";

	} 	

	if(x >= 800 && tablet==false) {

		whichDevice = "Desktop";

	} 

	return whichDevice;

}
       //sets the device type
	checkForMobile();

Found something better? , please let me know.