/frontend-react-best-practices

Do not wrap a simple expression with a primitive result type in useMemo

When an expression is simple (few logical or arithmetical operators) and has a primitive result type (boolean, number, string), do not wrap it in useMemo. Calling useMemo and comparing hook dependencies may consume more resources than the expression itself.

Incorrect:

function Header({ user, notifications }: Props) {
  let isLoading = useMemo(() => {
    return user.isLoading || notifications.isLoading;
  }, [user.isLoading, notifications.isLoading]);

  if (isLoading) return <Skeleton />;
  // return some markup
}

Correct:

function Header({ user, notifications }: Props) {
  let isLoading = user.isLoading || notifications.isLoading;

  if (isLoading) return <Skeleton />;
  // return some markup
}