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import { useState } from 'react';
import useStableMemo from './useStableMemo';
import useEffect from './useIsomorphicEffect';
import useEventCallback from './useEventCallback';
/**
* Setup an [`IntersectionObserver`](https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver) on
* a DOM Element that returns it's entries as they arrive.
*
* @param element The DOM element to observe
* @param init IntersectionObserver options with a notable change,
* unlike a plain IntersectionObserver `root: null` means "not provided YET",
* and the hook will wait until it receives a non-null value to set up the observer.
* This change allows for easier syncing of element and root values in a React
* context.
*/
/**
* Setup an [`IntersectionObserver`](https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver) on
* a DOM Element. This overload does not trigger component updates when receiving new
* entries. This allows for finer grained performance optimizations by the consumer.
*
* @param element The DOM element to observe
* @param callback A listener for intersection updates.
* @param init IntersectionObserver options with a notable change,
* unlike a plain IntersectionObserver `root: null` means "not provided YET",
* and the hook will wait until it receives a non-null value to set up the observer.
* This change allows for easier syncing of element and root values in a React
* context.
*
*/
function useIntersectionObserver(element, callbackOrOptions, maybeOptions) {
let callback;
let options;
if (typeof callbackOrOptions === 'function') {
callback = callbackOrOptions;
options = maybeOptions || {};
} else {
options = callbackOrOptions || {};
}
const {
threshold,
root,
rootMargin
} = options;
const [entries, setEntry] = useState(null);
const handler = useEventCallback(callback || setEntry);
// We wait for element to exist before constructing
const observer = useStableMemo(() => root !== null && typeof IntersectionObserver !== 'undefined' && new IntersectionObserver(handler, {
threshold,
root,
rootMargin
}), [handler, root, rootMargin, threshold && JSON.stringify(threshold)]);
useEffect(() => {
if (!element || !observer) return;
observer.observe(element);
return () => {
observer.unobserve(element);
};
}, [observer, element]);
return callback ? undefined : entries || [];
}
export default useIntersectionObserver;