const footer = window.document.getElementById('#footer'); const callback = function (entries, observer) { // Function executed when the intersection status changes }; // The observer object. It can be applied to multiple DOM elements const observer = new IntersectionObserver(callback, { rootMargin: "-10px 0px -10px 0px", }); if (footer !== null) { // Listen changes on a single element observer.observe(footer); // Stop listening a single element observer.unobserve(footer); // Stop listening all elements. observer.disconnect(); }