What is the difference between useMemo and useCallback?

What is the difference between useMemo and useCallback?

• A. useMemo returns a memoized function; useCallback returns a memoized value.
• B. useMemo and useCallback both return the same type of object.
• C. useMemo returns a memoized value; useCallback returns a memoized function.
• D. useMemo runs on every render; useCallback runs only on mount.

Answer: (C)

Memoization helps React avoid repeating work between renders. useMemo caches the result of an expensive computation and returns that same value on subsequent renders unless its dependencies change. useCallback does the same idea for functions: it returns the same function instance across renders until a dependency changes, so you can pass a stable callback to child components or hooks that rely on referential equality. So, the difference is that useMemo returns a memoized value, while useCallback returns a memoized function. They both depend on a dependencies array to decide when to recompute or recreate. The other options misstate this: one describes the return types incorrectly, and another falsely claims behavior about mounting versus rendering.

Memoization helps React avoid repeating work between renders. useMemo caches the result of an expensive computation and returns that same value on subsequent renders unless its dependencies change. useCallback does the same idea for functions: it returns the same function instance across renders until a dependency changes, so you can pass a stable callback to child components or hooks that rely on referential equality.

So, the difference is that useMemo returns a memoized value, while useCallback returns a memoized function. They both depend on a dependencies array to decide when to recompute or recreate. The other options misstate this: one describes the return types incorrectly, and another falsely claims behavior about mounting versus rendering.