Is on top scroll react shadow

is_top.js

  const [isTop, setIsTop] = useState(true)

  useEffect(() => {
    const handleScroll = () => {
      setIsTop(window.scrollY < 100)
    }

    window.addEventListener('scroll', handleScroll)

    return () => {
      window.removeEventListener('scroll', handleScroll)
    }
  }, [])