/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at
https://mozilla.org/MPL/2.0/. */
import { useEffect, useRef } from "react";
/**
* A custom react hook that sets up an IntersectionObserver to observe a single
* or list of elements and triggers a callback when the element comes into the viewport
* Note: The refs used should be an array type
* @function useIntersectionObserver
* @param {function} callback - The function to call when an element comes into the viewport
* @param {Object} options - Options object passed to Intersection Observer:
*
https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver/IntersectionObserver#options
* @param {Boolean} [isSingle = false] Boolean if the elements are an array or single element
*
* @returns {React.MutableRefObject} a ref containing an array of elements or single element
*
*
*
*/
function useIntersectionObserver(callback, threshold = 0.3) {
const elementsRef = useRef([]);
useEffect(() => {
const observer = new IntersectionObserver(
entries => {
entries.forEach(entry => {
if (entry.isIntersecting) {
callback(entry.target);
observer.unobserve(entry.target);
}
});
},
{ threshold }
);
elementsRef.current.forEach(el => {
if (el) {
observer.observe(el);
}
});
}, [callback, threshold]);
return elementsRef;
}
export { useIntersectionObserver };
