Build a Custom useIntersectionObserver Hook

Build a Custom useIntersectionObserver Hook

Implement a hook that tracks when an element enters/exits the viewport with proper TypeScript typing.

Solution:

function useIntersectionObserver(
  options: IntersectionObserverInit = {}
): [React.RefObject<HTMLElement>, IntersectionObserverEntry | null] {
  const [entry, setEntry] = useState<IntersectionObserverEntry | null>(null);
  const ref = useRef<HTMLElement>(null);
  
  useEffect(() => {
    const element = ref.current;
    if (!element) return;
    
    const observer = new IntersectionObserver(
      ([entry]) => setEntry(entry),
      options
    );
    
    observer.observe(element);
    
    return () => observer.disconnect();
  }, [options]);
  
  return [ref, entry];
}

// Usage
const MyComponent = () => {
  const [ref, entry] = useIntersectionObserver({
    threshold: 0.5,
    rootMargin: '0px'
  });
  
  return (
    <div ref={ref}>
      {entry?.isIntersecting ? 'Visible' : 'Hidden'}
    </div>
  );
};