$.fn.visible = function (partial) {
var $t = $(this),
$w = $(window),
viewTop = $w.scrollTop()+130, // 130 because fixed header
viewBottom = viewTop + $w.height(),
_top = $t.offset().top,
_bottom = _top + $t.height(),
compareTop = partial === true ? _bottom : _top,
compareBottom = partial === true ? _top : _bottom;
return compareBottom <= viewBottom && compareTop >= viewTop;
};
$(window).scroll(function (event) {
$(".vertical-scrolling").each(function (i, el) {
var el = $(el);
if (el.visible(true)) {
el.addClass("active");
} else {
el.removeClass("active");
}
});