React Native React Native State Management & Performance 2

Question 1

What does the useCallback hook optimize in React Native?

Accepted Answer

Memoizes callback functions to prevent unnecessary re-creation

Answer

useCallback returns a memoized version of a callback that only changes if its dependencies change, preventing child re-renders.

Question 2

What is the Hermes JavaScript engine and why is it used in React Native?

Accepted Answer

A lightweight JS engine optimized for React Native's performance

Answer

Hermes is a JavaScript engine built by Meta specifically for React Native, offering faster app startup and reduced memory usage.

Question 3

Which React Native optimization prevents unnecessary re-renders of functional components?

Accepted Answer

React.memo()

Answer

React.memo wraps a functional component and skips re-rendering if its props haven't changed, similar to PureComponent for classes.

Question 4

What causes unnecessary re-renders in React Native components?

Accepted Answer

Passing new object or function references as props on every render

Answer

Creating new object or function references on each render breaks referential equality checks, causing child components to re-render unnecessarily.

Question 5

What is the purpose of the useReducer hook?

Accepted Answer

To manage complex state logic using actions and a reducer function

Answer

useReducer is an alternative to useState for managing complex state transitions using a reducer function that handles action types.

React Native Practice Test