useEffect中获取之前的值

import React, { useEffect, useRef , useState} from "react";

const Test = () => {
  const [count] = useState(1);
  const prevCount = usePrevious(count);

  React.useEffect(() => {
    if (prevCount>count){
        console.log('count --')
    }
  }, [count]);

  return (
    <>
        pre：{prevCount}
        
        count：{count}
    </>
  );
};

export default Test;

function usePrevious(value) {
  const ref = useRef();

  useEffect(() => {
    ref.current = value;
  }, [value]);

  return ref.current;
}

参考文章：https://blog.csdn.net/qq_24724109/article/details/104053721