What is the purpose of useMemo() and useCallback() hooks?

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Purpose of useMemo()

The useMemo hook in React is used to optimize performance by memoizing (caching) the result of a calculation.

• It ensures that an expensive computation (like filtering a large list, or running a complex mathematical operation) is only re-executed when its dependencies change.

• If the dependencies remain the same, React reuses the previously stored result instead of recalculating.

• This avoids unnecessary re-renders and improves efficiency, especially in components that deal with heavy data processing.

In short: useMemo is for memoizing values.

Purpose of useCallback()

The useCallback hook is also for optimization, but instead of caching values, it memoizes functions.

• In React, functions are re-created on every render. Passing these newly created functions as props can cause child components to re-render unnecessarily.

• useCallback ensures that the same function instance is reused between renders, unless its dependencies change.

• This is very useful when working with child components wrapped in React.memo, or when functions are passed down to deeply nested components.

In short: useCallback is for memoizing functions.

✅ Simple way to remember:

• Use useMemo when you want to avoid recalculating values.

• Use useCallback when you want to avoid recreating functions.

Read More :

Explain the concept of Virtual DOM in React.

How do you implement conditional rendering in React?

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