Scroll direction for sticky header/footer, etc.

scroll-direction.js

window.addEventListener( 'DOMContentLoaded', ()=> {

	const	body = document.body,
		  	scrollUp = "scroll-up",
		  	scrollDown = "scroll-down",
		  	offset = 0;
	let 	lastScroll = window.pageYOffset;

	if ( lastScroll > offset ) {
		body.classList.add(scrollUp);
	}

	window.addEventListener('scroll', ()=> {

		const currentScroll = window.pageYOffset;
		
		if ( currentScroll <= offset ) {
			body.classList.remove(scrollUp);
			return;
		}
		if ( currentScroll > lastScroll && !body.classList.contains(scrollDown) ) {
			body.classList.remove(scrollUp);
			body.classList.add(scrollDown);
		} else if ( currentScroll < lastScroll && !body.classList.contains(scrollUp) ) {
			body.classList.remove(scrollDown);
			body.classList.add(scrollUp);
		}
		lastScroll = currentScroll;

	})

});