useEffect

const [Count, setCount] = useState(0)
const [Age, setAge] = useState(20)


useEffect(() => {
    if (Count != 0 && Count < 3) {
      setAge(Age + 1)
    }
  }, [Count])


<div>안녕하십니까 전 {Age}</div>
        <button
          onClick={() => {
            setCount(Count + 1)
          }}
        >
          누르면 먹기
        </button>
</div>