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React Hooks Quiz

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Question 1/15

What happens if a reference created with useRef changes?

Select your answer

The component will unmount.

The state gets reset.

The component will not immediately re-render.

The component will re-render.

Question 2/15

What is the useReducer hook used for in React?

Select your answer

Fetching data from APIs.

Managing side effects in components.

Rendering components conditionally.

State management that is more complex than useState.

Question 3/15

How do you perform cleanup after a component unmounts in useEffect?

useEffect(() => { return () => {/* cleanup code here */}; }, []);

Select your answer

Cleanup is automatic and requires no code.

Pass false as the second argument to useEffect.

Use a return statement within the useEffect callback function.

Use two consecutive useEffect hooks.

Question 4/15

What is a benefit of using useMemo in a functional component?

Select your answer

Always re-runs calculations when any render happens.

Automatically memorizes all local variables for optimization.

Reduces unnecessary calculations by caching a computed value unless its dependencies change.

Prevents all re-renders of the component.

Question 5/15

How can you update the current value of a ref object?

const myRef = useRef(initialValue);

Select your answer

myRef.current = newValue;

myRef = newValue;

setMyRef(newValue);

myRef.setValue(newValue);

Question 6/15

In useEffect, what does the cleanup function do?

Select your answer

It prevents the effect from running.

It does nothing, it's just a convention.

It runs before the component unmounts and when dependencies change.

It cleans up memory leaks.

Question 7/15

Which React hook can be used to run code after a component's render is complete?

Select your answer

useCallback

useMemo

useEffect

useRef

Question 8/15

Which hook can retain state-like value changes across renders but not cause re-renders?

Select your answer

useRef

useMemo

useState

useContext

Question 9/15

Which hook would you use to store the previous state of a prop or state?

Select your answer

useState

useEffect

useRef

useCallback

Question 10/15

What is the purpose of the useState hook in React?

Select your answer

To handle side effects in functional components.

To manage local component state within functional components.

To provide context to child components.

To access React lifecycle methods.

Question 11/15

When should you use the useContext hook?

Select your answer

To perform side effects.

To fetch remote data.

To manage component state.

To share values between components without passing them down manually through props.

Question 12/15

How can you persist a value between renders but prevent it from triggering a re-render?

Select your answer

useState

useRef

useReducer

useCallback

Question 13/15

What would happen if you omit the dependency array in useEffect?

Select your answer

The effect would run after every render, similar to componentDidUpdate.

The component would not unmount properly.

The effect would never run.

The effect would run once after the first render, similar to componentDidMount.

Question 14/15

Which hook will you use to optimize a React component by memoizing an expensive calculation?

Select your answer

useReducer

useEffect

useState

useMemo

Question 15/15

When should you avoid using useMemo?

Select your answer

In every component regardless of its needs.

For trivial calculations that do not significantly impact render performance.

For all calculations inside your component.

When calculations make the component throw errors.

Your Results

You did not answer any questions correctly.

Your Answers

Question 1/15

😊 Your answer was correct 🙁 Your answer was incorrect

What happens if a reference created with useRef changes?

Available answers

The component will unmount.

The state gets reset.

The component will not immediately re-render.

The component will re-render.

References created with useRef persist across renders but do not cause the component to re-render when they change.

Question 2/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is the useReducer hook used for in React?

Available answers

Fetching data from APIs.

Managing side effects in components.

Rendering components conditionally.

State management that is more complex than useState.

useReducer is used for state management, especially when state logic involves multiple sub-values or is complex. It is often used as an alternative to useState.

Question 3/15

😊 Your answer was correct 🙁 Your answer was incorrect

How do you perform cleanup after a component unmounts in useEffect?

useEffect(() => { return () => {/* cleanup code here */}; }, []);

Available answers

Cleanup is automatic and requires no code.

Pass false as the second argument to useEffect.

Use a return statement within the useEffect callback function.

Use two consecutive useEffect hooks.

To clean up effects, you can return a function from the useEffect effect callback, which React will run during the cleanup phase.

Question 4/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is a benefit of using useMemo in a functional component?

Available answers

Always re-runs calculations when any render happens.

Automatically memorizes all local variables for optimization.

Reduces unnecessary calculations by caching a computed value unless its dependencies change.

Prevents all re-renders of the component.

useMemo caches the result of an expensive calculation, preventing re-calculations unless one of the dependencies changes.

Question 5/15

😊 Your answer was correct 🙁 Your answer was incorrect

How can you update the current value of a ref object?

const myRef = useRef(initialValue);

Available answers

myRef.current = newValue;

myRef = newValue;

setMyRef(newValue);

myRef.setValue(newValue);

You can update a ref object by directly setting its current property, e.g., myRef.current = newValue.

Question 6/15

😊 Your answer was correct 🙁 Your answer was incorrect

In useEffect, what does the cleanup function do?

Available answers

It prevents the effect from running.

It does nothing, it's just a convention.

It runs before the component unmounts and when dependencies change.

It cleans up memory leaks.

The cleanup function returned by useEffect is executed before the component unmounts or before the effect is re-run to avoid resource leaks.

Question 7/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which React hook can be used to run code after a component's render is complete?

Available answers

useCallback

useMemo

useEffect

useRef

The useEffect hook allows you to perform side effects in function components and runs after the component renders.

Question 8/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which hook can retain state-like value changes across renders but not cause re-renders?

Available answers

useRef

useMemo

useState

useContext

The useRef hook maintains a persistent value across renders that can be changed without triggering a re-render.

Question 9/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which hook would you use to store the previous state of a prop or state?

Available answers

useState

useEffect

useRef

useCallback

useRef can be used to store mutable values across renders, including keeping track of previous props or states without causing re-renders.

Question 10/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is the purpose of the useState hook in React?

Available answers

To handle side effects in functional components.

To manage local component state within functional components.

To provide context to child components.

To access React lifecycle methods.

The useState hook is used to manage state in functional React components. It returns a state variable and a function to update that state.

Question 11/15

😊 Your answer was correct 🙁 Your answer was incorrect

When should you use the useContext hook?

Available answers

To perform side effects.

To fetch remote data.

To manage component state.

To share values between components without passing them down manually through props.

useContext allows you to access the current value of a context (created with React.createContext) across the component tree without prop drilling.

Question 12/15

😊 Your answer was correct 🙁 Your answer was incorrect

How can you persist a value between renders but prevent it from triggering a re-render?

Available answers

useState

useRef

useReducer

useCallback

useRef holds a value that persists across renders but does not cause re-renders when updated.

Question 13/15

😊 Your answer was correct 🙁 Your answer was incorrect

What would happen if you omit the dependency array in useEffect?

Available answers

The effect would run after every render, similar to componentDidUpdate.

The component would not unmount properly.

The effect would never run.

The effect would run once after the first render, similar to componentDidMount.

If the dependency array is omitted, useEffect defaults to running the effect after each render cycle, which can lead to performance issues if not intended.

Question 14/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which hook will you use to optimize a React component by memoizing an expensive calculation?

Available answers

useReducer

useEffect

useState

useMemo

useMemo is used to memoize expensive calculations based on dependencies, so they only re-calculate when necessary, thus optimizing performance.

Question 15/15

😊 Your answer was correct 🙁 Your answer was incorrect

When should you avoid using useMemo?

Available answers

In every component regardless of its needs.

For trivial calculations that do not significantly impact render performance.

For all calculations inside your component.

When calculations make the component throw errors.

useMemo is best avoided for trivial calculations as the optimization benefit is negated by the overhead of using the hook.