;(function ($) { $(window).load(function() { var theWindow = $(window), $bg = $("#bg-full"), aspectRatio = $bg.width() / $bg.height(); function resizeBg() { if ( (theWindow.width() / theWindow.height()) < aspectRatio ) { $bg .removeClass() .addClass('bgheight'); } else { $bg .removeClass() .addClass('bgwidth'); } } theWindow.resize(resizeBg).trigger("resize"); }); })(jQuery);