https://www.limbachinc.com/wp-content/themes/fildisi-child/js/HistoryTimeline/TimelineItem.js?ver=1

1class TimelineItem{
2	constructor(timelineItem){
3		this.timelineItem = timelineItem;
4		this.scrollToTop = this.getScrollTop();
5		this.isBlack = false;
6	}
7	
8	getScrollTop(){
9		// px number to top of viewport
10		const viewportTop = this.timelineItem.getBoundingClientRect().top;
11		const documentTop = document.body.getBoundingClientRect().top;
12		const scrollTopVal = viewportTop - documentTop;
13		return scrollTopVal;
14	}
15	
16	setScrollTop(scroll){
17		this.scrollToTop(scroll);
18	}
19	
20	changeColor(isOverSeparator){
21		return isOverSeparator?this.changeToBlack():this.changeToGray();
22	}
23	
24	changeToBlack(){
25		if(this.isBlack) return;
26		
27		this.timelineItem.classList.add('is-over-separator');
28		
29		this.isBlack = true;
30	}
31	
32	changeToGray(){
33		if(!this.isBlack) return;
34		
35		this.timelineItem.classList.remove('is-over-separator');
36		
37		this.isBlack = false;
38	}
39}