老师, 为什么本组件的useState 无法保存 oldTitle的状态

例如代码

  const [oldTitle, setOldTitle] = useState('');
  useEffect(() => {
    setOldTitle(document.title)
    console.log("oldTitle", oldTitle || 'not done')

  }, [])
  useEffect(() => {
    console.log("start", document.title || 'undefined')

    document.title = title;
    return () => {
      console.log("oldTitle", oldTitle);
      if (!keepOnceUnmounted) {
        document.title = oldTitle;
      }
    }
  }, [keepOnceUnmounted,  title])

是应为setOldTitle 和这里的useEffect里的return 都是一个时间戳的吗?
oldTitle 无法没被记录下来