useClickOutside — Detect Outside Clicks

import { useEffect, useRef, RefObject } from 'react';

export function useClickOutside<T extends HTMLElement>(
  onOutside: (e: MouseEvent | TouchEvent) => void
): RefObject<T> {
  const ref = useRef<T>(null);

  useEffect(() => {
    const handler = (e: MouseEvent | TouchEvent) => {
      if (ref.current && !ref.current.contains(e.target as Node)) {
        onOutside(e);
      }
    };
    document.addEventListener('mousedown', handler);
    document.addEventListener('touchstart', handler);
    return () => {
      document.removeEventListener('mousedown', handler);
      document.removeEventListener('touchstart', handler);
    };
  }, [onOutside]);

  return ref;
}

function Dropdown() {
  const [open, setOpen] = useState(false);
  const ref = useClickOutside<HTMLDivElement>(() => setOpen(false));
  return <div ref={ref}>{open && <Menu />}</div>;
}