Sentinels

gistfile1.txt

const menuPrimary = document.getElementById( 'menu-primary' );
const sentinelPrimary = document.querySelector( '.sentinel-primary' );
function handlerPrimary( entriesPrimary ){
	entriesPrimary.forEach( function( entry ){
		if( entry.isIntersecting ){
			menuPrimary.classList.remove( 'sticky' );
		} else {
			menuPrimary.classList.add( 'sticky' );
		}
	});
}
const observerPrimary = new window.IntersectionObserver( handlerPrimary );
observerPrimary.observe( sentinelPrimary );