Top 10 React.js useCallback() Interview Question

What is the useCallback hook in React?

It memoizes a callback function, preventing unnecessary re-creations on re-renders unless dependencies change.

What is the syntax of useCallback?

const memoizedCallback = useCallback(callback, [dependencies]);

Why would you use useCallback?

To optimize performance by memoizing functions passed as props to prevent unnecessary re-renders in child components.

How does useCallback differ from useMemo?

useCallback memoizes functions, while useMemo memoizes computed values.

When should you avoid using useCallback?

Avoid it for simple functions or when memoization doesn't provide significant performance benefits.

What happens if you omit the dependency array in useCallback?

The callback is re-created on every render, negating the memoization benefit.

Can useCallback improve performance in all cases?

No, it only helps when preventing unnecessary re-renders in components that rely on stable function references.

How does useCallback work with React's dependency array?

It re-creates the memoized function only when one or more dependencies change.

Can useCallback be used with inline functions?

Yes, but it’s typically used to memoize functions defined inline to maintain reference stability.

What is a common use case for useCallback?

Passing a stable callback to a child component or a hook like useEffect to avoid unnecessary re-renders or effects.