API do observador de interseção
let options = {
root: document.querySelector('#scrollArea'),
rootMargin: '0px',
threshold: 1.0
}
let observer = new IntersectionObserver(callback, options);
// A threshold of 1.0 means that when 100% of the target is
// visible within the element specified by the root option,
// the callback is invoked.
Creepy Caribou