Javascript 为什么 React.StrictMode 会中断计算props 状态的差异

function SchrödingersDiff()
{
  const [count, setCount] = useState(0);
  // simulate a changing state
  useEffect(() =>
  {
    const int = window.setInterval(() => setCount(s => s + 1), 1000);
    return () => window.clearInterval(int);
  }, []);

  const last = useRef(0);
  const diff = useMemo(() =>
  {
    const lastValue = last.current;
    last.current = count;
    const diff = count - lastValue;
    // console.log(diff);
    return diff;
  }, [count]);

  // console.log(diff);
  return diff;
}

为什么该组件在<React.StrictMode>以下运行时总是呈现"0"？它在没有严格模式的情况下工作良好(即渲染"1").

我知道strict模式会呈现两次，这可以解释它，但我希望useMemo会捕捉到这一点——事实确实如此:memo函数中的log每秒打印正确的"1".就连外面的那个也有.

有没有更好的方法来计算这个差异？

这是我实际的useState/useEffect/setInterval，已经调整为保留最后一个:

export function useChannel(channelName, initialData, currentOnly)
{
  const socket = useSc(s => s.socket); // gets a SocketCluster socket
  const [data, setData] = useState(currentOnly ? initialData : {current: initialData});

  useEffect(() =>
  {
    if (!socket) return;

    const channel = socket.subscribe(channelName);
    (async () =>
    {
      for await (const data of channel) setData(currentOnly ? data : s => ({current: data, last: s.current}));
    })();

    return () => channel.unsubscribe();
  }, [socket, channelName]);

  return data;
}