createIntersectionObserver.js
A wrapper function for creating new Intersection Observers.
/*!
* Create an intersection observer
* (c) 2021 Chris Ferdinandi, MIT License, https://gomakethings.com
* @param {Node} elem The element to observe
* @param {Function} callback The callback function to run
* @param {Object} options The options, if any
*/
function createIntersectionObserver (elem, callback, options) {
let observer = new IntersectionObserver(callback, options || {});
observer.observe(elem);
return observer;
}