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React Hooks Quiz

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Question 1/15

Suppose you want to prevent a child component from re-rendering unless necessary. Which hooks would aid in this optimization?

Select your answer

useEffect and useCallback

useCallback and useMemo

useState and useEffect

useReducer and useMemo

Question 2/15

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

The component would not unmount properly.

The effect would never run.

Question 3/15

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

Select your answer

useCallback

useRef

useEffect

useState

Question 4/15

How would you fetch data on component mount using useEffect?

useEffect(() => { fetchData(); }, []);

Select your answer

use useState to initiate a fetch on every render.

Pass an empty array as the second argument to run the effect once on component mount.

Run fetchData inside the component's return statement.

Pass null to the dependence array to always fetch data.

Question 5/15

How does useEffect handle updates based on specific value changes?

Select your answer

It requires specifying values in the dependency array.

It needs manual checks within the effect function.

It cannot handle updates based on specific values.

It automatically detects changes and updates.

Question 6/15

When should you use the useContext hook?

Select your answer

To fetch remote data.

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

To perform side effects.

To manage component state.

Question 7/15

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

Select your answer

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.

Always re-runs calculations when any render happens.

Question 8/15

What is the useReducer hook used for in React?

Select your answer

Rendering components conditionally.

Fetching data from APIs.

Managing side effects in components.

State management that is more complex than useState.

Question 9/15

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.

Use two consecutive useEffect hooks.

Use a return statement within the useEffect callback function.

Pass false as the second argument to useEffect.

Question 10/15

What hook would you use to reference a DOM node in a functional component?

Select your answer

useState

useRef

useMemo

useEffect

Question 11/15

Why might you use useCallback in React?

Select your answer

To clean up side effects.

To avoid re-rendering a component.

To manage state in a parent component.

To memorize a function so it doesn't change on every render unless dependencies change.

Question 12/15

When should you avoid using useMemo?

Select your answer

In every component regardless of its needs.

When calculations make the component throw errors.

For trivial calculations that do not significantly impact render performance.

For all calculations inside your component.

Question 13/15

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

Select your answer

useEffect

useMemo

useState

useReducer

Question 14/15

What is the purpose of the useState hook in React?

Select your answer

To access React lifecycle methods.

To manage local component state within functional components.

To handle side effects in functional components.

To provide context to child components.

Question 15/15

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

const myRef = useRef(initialValue);

Select your answer

myRef = newValue;

myRef.current = newValue;

setMyRef(newValue);

myRef.setValue(newValue);

Your Results

You did not answer any questions correctly.

Your Answers

Question 1/15

😊 Your answer was correct 🙁 Your answer was incorrect

Suppose you want to prevent a child component from re-rendering unless necessary. Which hooks would aid in this optimization?

Available answers

useEffect and useCallback

useCallback and useMemo

useState and useEffect

useReducer and useMemo

useCallback and useMemo can be used to memoize functions and values passed to children, thus avoiding unnecessary renders if they haven't changed.

Question 2/15

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

The component would not unmount properly.

The effect would never run.

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 3/15

😊 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

useCallback

useRef

useEffect

useState

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

Question 4/15

😊 Your answer was correct 🙁 Your answer was incorrect

How would you fetch data on component mount using useEffect?

useEffect(() => { fetchData(); }, []);

Available answers

use useState to initiate a fetch on every render.

Pass an empty array as the second argument to run the effect once on component mount.

Run fetchData inside the component's return statement.

Pass null to the dependence array to always fetch data.

Passing an empty array as the second argument ensures the effect only runs on component mount, similar to componentDidMount in class components.

Question 5/15

😊 Your answer was correct 🙁 Your answer was incorrect

How does useEffect handle updates based on specific value changes?

Available answers

It requires specifying values in the dependency array.

It needs manual checks within the effect function.

It cannot handle updates based on specific values.

It automatically detects changes and updates.

You can specify dependencies in the dependency array of useEffect. The effect runs only when these dependencies change.

Question 6/15

😊 Your answer was correct 🙁 Your answer was incorrect

When should you use the useContext hook?

Available answers

To fetch remote data.

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

To perform side effects.

To manage component state.

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

Question 7/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

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.

Always re-runs calculations when any render happens.

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

Question 8/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is the useReducer hook used for in React?

Available answers

Rendering components conditionally.

Fetching data from APIs.

Managing side effects in components.

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 9/15

😊 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.

Use two consecutive useEffect hooks.

Use a return statement within the useEffect callback function.

Pass false as the second argument to useEffect.

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

Question 10/15

😊 Your answer was correct 🙁 Your answer was incorrect

What hook would you use to reference a DOM node in a functional component?

Available answers

useState

useRef

useMemo

useEffect

useRef can be used to directly access a DOM node or React element after a component has rendered.

Question 11/15

😊 Your answer was correct 🙁 Your answer was incorrect

Why might you use useCallback in React?

Available answers

To clean up side effects.

To avoid re-rendering a component.

To manage state in a parent component.

To memorize a function so it doesn't change on every render unless dependencies change.

useCallback memorizes a function and returns a memoized version of it that changes only if one of the dependencies has changed, which can help with optimization.

Question 12/15

😊 Your answer was correct 🙁 Your answer was incorrect

When should you avoid using useMemo?

Available answers

In every component regardless of its needs.

When calculations make the component throw errors.

For trivial calculations that do not significantly impact render performance.

For all calculations inside your component.

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

Question 13/15

😊 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

useEffect

useMemo

useState

useReducer

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

Question 14/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is the purpose of the useState hook in React?

Available answers

To access React lifecycle methods.

To manage local component state within functional components.

To handle side effects in functional components.

To provide context to child components.

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 15/15

😊 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 = newValue;

myRef.current = newValue;

setMyRef(newValue);

myRef.setValue(newValue);

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