react usecallback

1/*
2	A common use case is to access a child imperatively: 
3*/
4
5function TextInputWithFocusButton() {
6  const inputEl = useRef(null);
7  const onButtonClick = () => {
8    // `current` points to the mounted text input element
9    inputEl.current.focus();
10  };
11  return (
12    <>
13      <input ref={inputEl} type="text" />
14      <button onClick={onButtonClick}>Focus the input</button>
15    </>
16  );
17}

1// They both take a function and an array of dependencies:
2
3useCallback(() => {···}, [dependency1, dependency2]);
4useMemo(() => {···}, [dependency1, dependency2]);
5
6// So what is the difference? 
7
8// useCallback returns its function uncalled so you can call it later
9// therefore, it gives you back the function's reference
10
11// useMemo calls its function and returns the result.
12// therefore, it gives you back the function's return value
13

1const memoizedCallback = useCallback(
2  () => {
3    doSomething(a, b);
4  },
5  [a, b],
6);