Add a body class when user begins scrolling using jQuery.
(function($){
$(document).ready(function(){
// Add class to body when scrolling to add white background
var targetDiv = $('body');
$(window).scroll(function() {
var windowpos = $(window).scrollTop();
// change amount here to choose distance from top to add class
if( windowpos >= 50 ) {
targetDiv.addClass('scrolling-active');
} else {
targetDiv.removeClass('scrolling-active');
}
});
});
})(jQuery);