scrollhandler.js

document.addEventListener("scroll", scrollHandler, true);

function scrollHandler() {

	currentScrollPosition = document.documentElement.scrollTop;	

	for (var i=1; i<=positionArray.length; i++){

		if (currentScrollPosition>=positionArray[i-1] && currentScrollPosition < positionArray[i]) {

			var currentActive = document.getElementsByClassName('is-active')[0];

				if (currentActive != undefined){
			currentActive.classList.remove('is-active');
		}
			
			quickLinks[i-1].classList.add('is-active');

			break;

		}

		if (currentScrollPosition>positionArray[positionArray.length-1]){
			var currentActive = document.getElementsByClassName('is-active');


				var currentActive = document.getElementsByClassName('is-active')[0];

				if (currentActive != undefined){
			currentActive.classList.remove('is-active');
			}
			quickLinks[quickLinks.length-1].classList.add('is-active');

			break;

		}
	}
};