JQuery ajax blog loader

//lazyload
 
var page = 1;
var loading = false;
minus = 40;
if((navigator.userAgent.match(/iPhone/i))) minus = 240; 
 
$(window).scroll(function() {
	if($(window).scrollTop() >= $(document).height() - $(window).height() - minus){
           page ++;
           nextPage();
       	}
});
 
function nextPage() {
	if(loading) return;
	$('#postHolder').append('<div id="blog_preloader"></div>');
	loading = true;
 
	jQuery.ajax({
		type: "GET",
     		data: 'page=' + page,
        	url: "/ajax-file.php",
        	success: function(results) {
           		$(results).appendTo('#postHolder');
           		$('#blog_preloader').remove();
           		loading = false;
        	}
    	});
}