React Performance Optimization: Memoization

useMemo is for class components, useCallback is for functional components
useMemo works with useEffect, useCallback doesn't
useMemo memoizes returned values, useCallback memoizes functions
The key difference is that useMemo memoizes returned values while useCallback memoizes functions. useMemo is used to memoize the result of a computation (like `useMemo(() => computeExpensiveValue(a, b), [a, b])`), whereas useCallback is used to memoize a function definition itself (like `useCallback(() => { doSomething(a, b) }, [a, b])`). useCallback(fn, deps) is equivalent to useMemo(() => fn, deps).
useMemo is faster than useCallback