What is the difference between useMemo and useCallback in React?

The hooks useMemo and useCallback in React are both used to optimize performance, but they have slightly different use cases and effects.

1. Remember:
2. Purpose: used to cache computation results and avoid repeated computation.
3. Scenario: When a certain calculation takes a long time, but the result remains stable when the dependencies do not change, useMemo can be used to cache the calculation results, avoiding unnecessary repeated calculations.
4. Syntax: const memoizedValue = useMemo(() => computeExpensiveValue(a, b), [a, b]);, passing in a function and an array of dependencies, the value will only be recalculated when the dependencies change.
5. Return value: returns the calculated result.
6. Function to call back.
7. Purpose: used to cache callback functions to avoid unnecessary re-creation.
8. Scenario: When a component needs to pass a callback function as a prop to a child component, you can use useCallback to cache the callback function and prevent unnecessary re-renders of the child component.
9. Syntax: const memoizedCallback = useCallback(() => { doSomething(a, b); }, [a, b]);, passing in a callback function and an array of dependencies, the callback function will only be recreated when the dependencies change.
10. Return value: Return the cached callback function.

In summary:

1. useMemo is used to cache computation results for situations where the computation is time-consuming and the result is stable.
2. The useCallback is used to cache callback functions, especially when you need to pass a callback function as a property to a child component.