React useMemo与useCallabck有什么区别

const memoizedValue = useMemo(() => computeExpensiveValue(a, b), [a, b]);

const memoizedCallback = useCallback(
  () => {
    doSomething(a, b);
  },
  [a, b],
);

 /**
     * `useMemo` will only recompute the memoized value when one of the `deps` has changed.
     *
     * @version 16.8.0
     * @see https://reactjs.org/docs/hooks-reference.html#usememo
     */
    // allow undefined, but don't make it optional as that is very likely a mistake
    function useMemo<T>(factory: () => T, deps: DependencyList | undefined): T;
 /**
     * `useCallback` will return a memoized version of the callback that only changes if one of the `inputs`
     * has changed.
     *
     * @version 16.8.0
     * @see https://reactjs.org/docs/hooks-reference.html#usecallback
     */
    // A specific function type would not trigger implicit any.
    // See https://github.com/DefinitelyTyped/DefinitelyTyped/issues/52873#issuecomment-845806435 for a comparison between `Function` and more specific types.
    // tslint:disable-next-line ban-types
    function useCallback<T extends Function>(callback: T, deps: DependencyList): T;

import React, { FC, useCallback, useMemo, useState } from 'react';
const Index: FC = (props) => {
  const [count, setCount] = useState(0);
  const isEvenNumber = useMemo(() => {
    return count % 2 === 0;
  }, [count]);
  const onClick = useCallback(() => {
    setCount(count + 1);
  }, [count]);
  return (
    <div>
      <div>{count} is {isEvenNumber ？ 'even':'odd'} number</div>
      <button onClick={onClick}></button>
    </div>
  );
};