jQuery(document).ready(function($) { $('.state_0').addClass('state_1'); function checkVisibility() { $('.animate-element').each(function() { var windowHeight = $(window).height(); var windowTopPosition = $(window).scrollTop(); var windowBottomPosition = (windowTopPosition + windowHeight); var element = $(this); var elementHeight = element.outerHeight(); var elementTopPosition = element.offset().top; var elementBottomPosition = (elementTopPosition + elementHeight); // Check if the element is within the viewport if ((elementBottomPosition >= windowTopPosition) && (elementTopPosition <= windowBottomPosition)) { element.addClass('in-viewport'); } }); } checkVisibility(); $(window).on('scroll', function() { checkVisibility(); // Check visibility during scrolling }); });