reactjs - Using useMemo instead of React.memo syntax issue

Question

I need to make a demonstration of using React Hooks useMemo. I have working code that is as follows that does what I want:

const SpeakerCardDetail = React.memo(
  ({id,...

I found a link that shows that I could use syntax more like this but I can't figure it out exactly.

This is as far as I got:

const SpeakerDetail = React.useMemo(() => {
   ({ id,

Clearly not it though. I do get that React.memo solves the problem but I do need to show useMemo in action and am hoping there is an alternative syntax that I can use.

Answer 1

React.memo and React.useMemo are not equivalent at all (don't rely on naming similarity). Here's a quote from React.memo doc:

React.memo is a higher order component.

So it's a HOC that can optimize rendition of your component given that it renders the same output with the same properties.

React.useMemo on the other hand is more generic and returns a memoized value:

Pass a “create” function and an array of dependencies. useMemo will only recompute the memoized value when one of the dependencies (either a or b) has changed.

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

And while it can be hacked to be used instead of React.memo, it's not its purpose and it will add to the confusion more than it will help. useMemo is a hook and is subject to the certain usage rules.

And there's this warning as well:

In the future, React may choose to “forget” some previously memoized values and recalculate them on next render, e.g. to free memory for offscreen components. Write your code so that it still works without useMemo — and then add it to optimize performance.