intersection-observer-api.js

// const options = {
//   root: document.querySelector('.ct-inner-content'),
//   rootMargin: '0px',
//   threshold: 1.0
// }

const div = document.querySelector("#div_id");

const options = {}

let callback = (entries, observer) => {
	entries.forEach(entry => {
		// Add 'active' class if observation target is inside viewport
		if (entry.intersectionRatio > 0) {
			console.log(entry.target);
			entry.target.classList.toggle("animate__animated", "animate__fadeInUp");
		}
		// Remove 'active' class otherwise
		else {
		  entry.target.classList.remove("animate__animated", "animate__fadeInUp");
		}
	});
}

let observer = new IntersectionObserver(callback, options);

observer.observe(div);