const [isScroll, setScroll] = useState(false);
  
  const onScroll = () => {
    
    
    let scrolled =
      document.documentElement.scrollTop || document.body.scrollTop;
    setScroll(scrolled); //滚动条位置
  };

  useEffect(() => {
    
    
    document.addEventListener("scroll", onScroll);
    return () => {
    
    
      document.removeEventListener("scroll", onScroll);
    };
  }, []);