IntersectionObserver

const header = document.querySelector('.header');
const navHeight = nav.getBoundingClientRect().height; const stickyNav = function (entries) { const [entry] = entries; // entries[0] if (!entry.isIntersecting) nav.classList.add('sticky'); else nav.classList.remove('sticky');
}; const headerObserver = new IntersectionObserver(stickyNav, { root: null, threshold: 0, rootMargin: `-${navHeight}px`,
});
headerObserver.observe(header);

const initialCoords = section1.getBoundingClientRect() window.addEventListener('scroll', function(e) { console.log(window.scrollY); if(window.scrollY > initialCoords.top) nav.classList.add('sticky'); else nav.classList.remove('sticky') }) const obsCallback = function (entries, observer) { entries.forEach(entry => { console.log(entry); });
}; const obsOptions = { root: null, threshold: [0, 0.2], // [0, 1, 0.2] (100%)
};