useMemo#

1import { useMemo } from "react";
2import { useState } from "react";
3
4export default function App() {
5  const [num, setNum] = useState(0);
6  let total = useMemo(() => {
7    return num * 2;
8  }, [num]);
9  return (
10    <div>
11      <p>{num}</p>
12      <p>{total}</p>
13      <button
14        onClick={() => {
15          setNum(num + 1);
16        }}
17      >
18        按钮
19      </button>
20    </div>
21  );
22}