https://fliegermuseum.ch/wp-content/plugins/essential-addons-elementor/assets/js/vertical-timeline.js?ver=1.0

1jQuery(document).ready(function($){
2	var timelineBlocks = $('.eael-content-timeline-block'),
3		offset = 0.8;
4
5	//hide timeline blocks which are outside the viewport
6	hideBlocks(timelineBlocks, offset);
7
8	//on scolling, show/animate timeline blocks when enter the viewport
9	$(window).on('scroll', function(){
10		(!window.requestAnimationFrame)
11			? setTimeout(function(){ showBlocks(timelineBlocks, offset); }, 100)
12			: window.requestAnimationFrame(function(){ showBlocks(timelineBlocks, offset); });
13	});
14
15	function hideBlocks(blocks, offset) {
16		blocks.each(function(){
17			( $(this).offset().top > $(window).scrollTop()+$(window).height()*offset ) && $(this).find('.eael-content-timeline-img, .eael-content-timeline-content').addClass('is-hidden');
18		});
19	}
20
21	function showBlocks(blocks, offset) {
22		blocks.each(function(){
23			( $(this).offset().top <= $(window).scrollTop()+$(window).height()*offset && $(this).find('.eael-content-timeline-img').hasClass('is-hidden') ) && $(this).find('.eael-content-timeline-img, .eael-content-timeline-content').removeClass('is-hidden').addClass('');
24		});
25	}
26
27	/**
28	 * Timeline Animation Script
29	 */
30	var getElementsInArea = (function(docElm){
31	    var viewportHeight = docElm.clientHeight;
32
33	    return function(e, opts){
34	        var found = [], i;
35
36	        if( e && e.type == 'resize' )
37	            viewportHeight = docElm.clientHeight;
38
39	        for( i = opts.elements.length; i--; ){
40	            var elm        = opts.elements[i],
41	                pos        = elm.getBoundingClientRect(),
42	                topPerc    = pos.top    / viewportHeight * 100,
43	                bottomPerc = pos.bottom / viewportHeight * 100,
44	                middle     = (topPerc + bottomPerc)/2,
45	                inViewport = middle > opts.zone[1] &&
46	                             middle < (100-opts.zone[1]);
47
48	            elm.classList.toggle(opts.markedClass, inViewport);
49
50	            if( inViewport )
51	                found.push(elm);
52	        }
53	    };
54	})(document.documentElement);
55
56	/**
57	 * Use Case
58	 */
59	window.addEventListener('scroll', f)
60	window.addEventListener('resize', f)
61
62	function f(e){
63	    getElementsInArea(e, {
64	        elements    : document.querySelectorAll('.eael-content-timeline-block'),
65	        markedClass : 'highlight',
66	        zone        : [15, 15] // percentage distance from top & bottom
67	    });
68	}
69});