Loading... Login Loading... Register

React State Management Quiz

Want to learn more than this quiz offers you? Have a look at my Frontend web development courses.

Create an account and save your quiz results

Login and save your results

First Name *

Last Name *

Email *

Password *

Confirm Password *

I agree to the Terms of Service & Privacy Policy.

Add me to your newsletter.

Question 1/15

Why is the concept of immutable state vital in Redux?

Select your answer

It allows CSS to adjust automatically with state changes.

It ensures predictability and verifiability of application state.

It integrates directly into Vue.js applications.

The mutable state causes React to throw errors.

Question 2/15

What does the Provider component in a Redux application do?

Select your answer

Connects to external APIs to fetch initial state.

Injects the Redux store into the React component tree.

Memorizes static props across re-renders.

Wraps the event handling logic for the application.

Question 3/15

In React, what is the main benefit of lifting state up?

Select your answer

To enable JSX to be converted to strings.

To enable two sibling components to share and sync state.

To reduce execution context in large applications.

To add more states directly to child components.

Question 4/15

In a React functional component, what is the correct way to update a state variable that holds an object?

const [user, setUser] = useState({ name: 'John', age: 30 });

Select your answer

setUser({ ...user, name: 'Jane' });

setUser(user => user.name = 'Jane');

user.name = 'Jane'; setUser(user);

setUser({ name: 'Jane', age: 32 });

Question 5/15

What mechanism does Redux use to update its state?

Select your answer

Components directly mutate the store object.

Reducers compute a new state based on actions dispatched.

Action creators update the global state through context managers.

The state is serialized and written into session storage upon updates.

Question 6/15

Consider the following Redux action. What is its primary purpose?

const fetchData = () => ({ type: 'FETCH_DATA' });

Select your answer

To update the component styles.

To reset the global store to its initial state.

To directly mutate the Redux store state.

To initiate a side effect, like data fetching from an API.

Question 7/15

What is the common way to improve performance for a component consistently re-rendering due to state changes?

Select your answer

Increase the delay between re-renders

Use

React.memo

to wrap the component

Limit the number of state variables

Publish the component in a separate thread

Question 8/15

When is it recommended to use useCallback in React?

Select your answer

When you render a list of elements with dynamic keys.

When you want to dispatch actions within Redux reducers.

When you want to memoize a function to prevent unnecessary re-creation.

When you need to attach a ref to a DOM element.

Question 9/15

Which of the following concepts does NOT involve React component state management?

Select your answer

Context API

CSS-in-JS Libraries like Emotion

useState hook

Redux

Question 10/15

Why should keys be unique among siblings in React?

Select your answer

To help React identify which items have changed, are added, or are removed.

To establish the context of an application route.

To enable asynchronous data loading.

To provide names to variables within render methods.

Question 11/15

What is React's useEffect hook used for?

Select your answer

To directly update the DOM manually.

To optimize component rendering performance.

To initialize state in class components.

To perform side effects in function components.

Question 12/15

When handling forms in React, why is controlled component considered best practice?

Select your answer

Because it synchronizes the input data with the component's state.

Asynchronous JavaScript functions can execute during creation.

It uses HTML validation for form inputs.

CSS styles are automatically applied to form elements.

Question 13/15

How can you prevent unnecessary re-renders in a component that uses React Context?

Select your answer

By using React.memo in combination with React Context

By using a higher-order component strictly

By wrapping the component in a

shouldComponentUpdate

method

By storing state outside of React components

Question 14/15

In Redux, what is a pure function in terms of reducers?

Select your answer

A function that fetches data from an API and updates the global state.

A function that depends on input and generates the same output without any side effects.

A function that has access to the local component state.

A function which can modify its arguments or outside variables.

Question 15/15

Consider the following use of useEffect. When does the effect run?

useEffect(() => { console.log('Updated!'); }, [count]);

Select your answer

Only once, when the component mounts.

Every time the component re-renders.

Whenever the 'count' state changes.

Never, because 'useEffect' is not properly configured.

Your Results

You did not answer any questions correctly.

Your Answers

Question 1/15

😊 Your answer was correct 🙁 Your answer was incorrect

Why is the concept of immutable state vital in Redux?

Available answers

It allows CSS to adjust automatically with state changes.

It ensures predictability and verifiability of application state.

It integrates directly into Vue.js applications.

The mutable state causes React to throw errors.

Maintaining an immutable state in Redux ensures predictability and verifiability. Each state change creates a new copy of the state, ensuring that changes are explicit and the application state remains predictable, which simplifies debugging.

Question 2/15

😊 Your answer was correct 🙁 Your answer was incorrect

What does the Provider component in a Redux application do?

Available answers

Connects to external APIs to fetch initial state.

Injects the Redux store into the React component tree.

Memorizes static props across re-renders.

Wraps the event handling logic for the application.

The Provider component from the react-redux library makes the Redux store available to the rest of the app. By wrapping the application's component tree, it provides components with the ability to connect to the Redux store.

Question 3/15

😊 Your answer was correct 🙁 Your answer was incorrect

In React, what is the main benefit of lifting state up?

Available answers

To enable JSX to be converted to strings.

To enable two sibling components to share and sync state.

To reduce execution context in large applications.

To add more states directly to child components.

Lifting state up in React involves moving shared state to a common ancestor component, allowing different sibling components to access and sync the state. This approach supports better data flow and state management across components.

Question 4/15

😊 Your answer was correct 🙁 Your answer was incorrect

In a React functional component, what is the correct way to update a state variable that holds an object?

const [user, setUser] = useState({ name: 'John', age: 30 });

Available answers

<pre><code>setUser({ ...user, name: 'Jane' });</code></pre>

<pre><code>setUser(user => user.name = 'Jane');</code></pre>

<pre><code>user.name = 'Jane'; setUser(user);</code></pre>

<pre><code>setUser({ name: 'Jane', age: 32 });</code></pre>

When updating a state variable that holds an object in React, you should use the spread operator to create a new object with the updated fields. The option

setUser({ ...user, name: 'Jane' });

creates a new object with the existing properties from user and only changes the name property.

Question 5/15

😊 Your answer was correct 🙁 Your answer was incorrect

What mechanism does Redux use to update its state?

Available answers

Components directly mutate the store object.

Reducers compute a new state based on actions dispatched.

Action creators update the global state through context managers.

The state is serialized and written into session storage upon updates.

Redux alters its global state using reducers, which are pure functions. Upon receiving an action dispatched by action creators, these reducers compute and return a new state based on the previous state and the action.

Question 6/15

😊 Your answer was correct 🙁 Your answer was incorrect

Consider the following Redux action. What is its primary purpose?

const fetchData = () => ({ type: 'FETCH_DATA' });

Available answers

To update the component styles.

To reset the global store to its initial state.

To directly mutate the Redux store state.

To initiate a side effect, like data fetching from an API.

In Redux, actions are payloads of information that send data from your application to your store. The action

{ type: 'FETCH_DATA' }

typically represents indicating the initiation of a side effect such as fetching data from an external API.

Question 7/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is the common way to improve performance for a component consistently re-rendering due to state changes?

Available answers

Increase the delay between re-renders

Use <pre><code>React.memo</code></pre> to wrap the component

Limit the number of state variables

Publish the component in a separate thread

To prevent unnecessary re-renders due to the same props and state in a React component, wrapping the component with React.memo optimizes performance by memoizing the rendered output unless there are meaningful prop changes.

Question 8/15

😊 Your answer was correct 🙁 Your answer was incorrect

When is it recommended to use useCallback in React?

Available answers

When you render a list of elements with dynamic keys.

When you want to dispatch actions within Redux reducers.

When you want to memoize a function to prevent unnecessary re-creation.

When you need to attach a ref to a DOM element.

The useCallback hook in React is recommended when you have a function that needs to retain the same instance between renders, preventing unnecessary re-creations especially when passing it as a prop to child components that could result in unneeded renders.

Question 9/15

😊 Your answer was correct 🙁 Your answer was incorrect

Which of the following concepts does NOT involve React component state management?

Available answers

Context API

CSS-in-JS Libraries like Emotion

useState hook

Redux

CSS-in-JS libraries, although used widely with React for styling components, primarily deal with styling rather than state management. On the other hand, useState, Redux, and Context API are directly related to managing state within React applications.

Question 10/15

😊 Your answer was correct 🙁 Your answer was incorrect

Why should keys be unique among siblings in React?

Available answers

To help React identify which items have changed, are added, or are removed.

To establish the context of an application route.

To enable asynchronous data loading.

To provide names to variables within render methods.

Keys are vitally important in React as they help identify which items have changed, are added, or removed among a collection of sibling elements. They must be unique among their siblings but can be duplicated across different sets of sibling elements.

Question 11/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is React's useEffect hook used for?

Available answers

To directly update the DOM manually.

To optimize component rendering performance.

To initialize state in class components.

To perform side effects in function components.

The useEffect hook in React is used for performing side effects in function components, such as data fetching, subscriptions, or manually changing the DOM. It replaces the side-effect features of lifecycle methods in class components.

Question 12/15

😊 Your answer was correct 🙁 Your answer was incorrect

When handling forms in React, why is controlled component considered best practice?

Available answers

Because it synchronizes the input data with the component's state.

Asynchronous JavaScript functions can execute during creation.

It uses HTML validation for form inputs.

CSS styles are automatically applied to form elements.

Controlled components in React refer to form elements being controlled by React state. This approach ensures that the rendered form is always in sync with the component's state, providing better control over data submission, validation, and component behavior.

Question 13/15

😊 Your answer was correct 🙁 Your answer was incorrect

How can you prevent unnecessary re-renders in a component that uses React Context?

Available answers

By using React.memo in combination with React Context

By using a higher-order component strictly

By wrapping the component in a <pre><code>shouldComponentUpdate</code></pre> method

By storing state outside of React components

Using React.memo helps to prevent unnecessary re-renders by memoizing the component if its props have not changed. While using React Context, wrapping the consumer component with React.memo can help improve performance by avoiding renders that are triggered even if the consumed context value did not change.

Question 14/15

😊 Your answer was correct 🙁 Your answer was incorrect

In Redux, what is a pure function in terms of reducers?

Available answers

A function that fetches data from an API and updates the global state.

A function that depends on input and generates the same output without any side effects.

A function that has access to the local component state.

A function which can modify its arguments or outside variables.

Reducers in Redux are pure functions. This means they always return the same output for a given input and do not produce side effects like data fetching or mutations outside their scope. The intention is to maintain predictable state transformations.

Question 15/15

😊 Your answer was correct 🙁 Your answer was incorrect

Consider the following use of useEffect. When does the effect run?

useEffect(() => { console.log('Updated!'); }, [count]);

Available answers

Only once, when the component mounts.

Every time the component re-renders.

Whenever the 'count' state changes.

Never, because 'useEffect' is not properly configured.

The useEffect hook takes a dependency array as its second argument. In this case,

[count]

means the effect will run every time the count state changes.