intersectionobserver.js

intersectionobserver.js

let options = {
  root: document.querySelector("#scrollArea"), // null
  rootMargin: "0px 0px 0px 0px",
  threshold: 1.0 // [0, 0.25, 0.50, 0.75, 1]
};
let observer = new IntersectionObserver(callback, options);
let target = document.querySelector("#listItem");
observer.observe(target);
observer.unobserve(target);