/**
 * Hook that uses `IntersectionObserver` to trigger `onIntersect` callback when element is in viewport.
 * Callback is called only once by default (can be changed using the `once` parameter).
 * @returns a callback ref that needs to be set on the element you want to observe.
 * @private
 * @example
 * const onIntersection = React.useCallback(() => {
 *   console.log('Element is in viewport!');
 * }, []);
 * const ref = useIntersection(onIntersection);
 * return (<div ref={ref}>One of many elements</div>);
 */
export declare const useIntersection: (onIntersect: () => void, options?: IntersectionObserverInit, once?: boolean) => (node: HTMLElement | null) => void;