Executes function whenever there's an orientation change (i.e. rotating a smartphone/tablet)

detectOrientation.js

$(window).bind('orientationchange', function(){
  // do whatever
});

// The below will give you the current orientation for iOS devices, possible values being 0, 90, -90 or 180 (180 on iPad only)
if (navigator.userAgent.match(/(iPod|iPhone|iPad)/)) {
  	alert(window.orientation);
}