Quiz for Memoization

Q1: What is memoization in React?

A. Caching results of expensive function calls B. Rendering components repeatedly C. Updating state frequently D. Using CSS for styling

Q2: Which React hook is used for memoizing a component?

A. React.memo B. useState C. useEffect D. useRef

Q3: How does React.memo improve performance?

A. Prevents re-render if props have not changed B. Always re-renders component C. Deletes component state D. Delays rendering

Q4: Which hook memoizes a value?

A. useMemo B. useState C. useCallback D. useEffect

Q5: Which hook memoizes a callback function?

A. useCallback B. useState C. useMemo D. useRef

Q6: When should you use useMemo?

A. To memoize expensive calculations B. Always C. Never D. Only in class components

Q7: What problem does memoization solve?

A. Unnecessary re-rendering and recalculations B. Slow API calls C. Styling issues D. Memory leaks

Q8: Can React.memo memoize functional components?

A. Yes B. No C. Only class components D. Only hooks

Q9: What is a limitation of React.memo?

A. Only shallow compares props B. Deeply compares all nested objects C. Memoizes state D. Changes state automatically

Q10: How to customize React.memo comparison?

A. Pass a custom comparison function as second argument B. Use default only C. Change state D. Use useEffect

Q11: Does useMemo guarantee memoization?

A. No, it is a performance optimization hint B. Yes, always C. No, it never memoizes D. Only in dev mode

Q12: What is the difference between useMemo and useCallback?

A. useMemo memoizes values, useCallback memoizes functions B. Both memoize values C. Both memoize functions D. Both memoize state

Q13: How can useCallback improve child component performance?

A. Prevents child re-render when function props don’t change B. Always re-renders child C. Deletes child state D. Changes child props

Q14: Is memoization always beneficial?

A. No, it can add complexity and overhead if used unnecessarily B. Yes, always beneficial C. No, never use memoization D. Only in production

Q15: What does shallow comparison mean?

A. Comparing only first-level properties B. Comparing deeply nested objects C. Comparing function outputs D. Comparing styles

Q16: How does useMemo help with expensive computations?

A. Caches computation between renders B. Recomputes every render C. Blocks UI D. Changes state automatically

Q17: Can useMemo memoize asynchronous functions?

A. No, it memoizes values synchronously B. Yes, fully supports async C. Sometimes D. Only with promises

Q18: What should you pass as dependencies to useMemo?

A. Variables that affect the memoized value B. Empty array always C. State variables only D. No dependencies

Q19: What is a common pitfall when using useMemo?

A. Using it for cheap computations B. Not using it at all C. Using only with state D. Using with props

Q20: Which React feature works hand-in-hand with memoization?

A. Pure components B. Class components C. Strict mode D. Fragments