Super small (just 0.1KB) jQuery plugin to add a class when scrolling past a certain point.
<script src="sticky.min.js"></script>Add the class my-class to the element with id my-element when the visitor scrolls past 50px from the page top. The class will automatically be removed when scrolling back past the trigger.
$('#my-element').sticky(50, 'my-class');Same as above, but triggered when the element is about to be scrolled past.
var elementY = $('#my-element').offset().top;
$('#my-element').sticky(elementY, 'my-class');