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React State Management Quiz

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Question 1/15

What does the Provider component in a Redux application do?

Select your answer

Injects the Redux store into the React component tree.

Wraps the event handling logic for the application.

Memorizes static props across re-renders.

Connects to external APIs to fetch initial state.

Question 2/15

What is the default behavior of Context in React regarding re-renders?

Select your answer

The components using Context never re-render.

It causes re-renders whenever the Provider's value changes.

It causes re-renders depending on the content of the values, not structural change.

It only re-renders the component where the Context is defined.

Question 3/15

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 4/15

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

Select your answer

Use

React.memo

to wrap the component

Increase the delay between re-renders

Limit the number of state variables

Publish the component in a separate thread

Question 5/15

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 6/15

What is the primary purpose of React's useState hook?

const [count, setCount] = useState(0);

Select your answer

To manage component state within functional components

To fetch data from a remote server

To handle form submissions in react

To navigate between routes in a React application

Question 7/15

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

Select your answer

A function that has access to the local component state.

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

A function which can modify its arguments or outside variables.

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

Question 8/15

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 provide names to variables within render methods.

To establish the context of an application route.

To enable asynchronous data loading.

Question 9/15

What is React's useEffect hook used for?

Select your answer

To directly update the DOM manually.

To perform side effects in function components.

To optimize component rendering performance.

To initialize state in class components.

Question 10/15

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 11/15

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 12/15

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

Select your answer

To enable two sibling components to share and sync state.

To enable JSX to be converted to strings.

To add more states directly to child components.

To reduce execution context in large applications.

Question 13/15

What problem does React Context API primarily solve?

Select your answer

Global style management

Passing data through a simple component tree without prop drilling

Routing between components

Reducing state updates from asynchronous actions

Question 14/15

What does the useRef hook in React primarily serve?

Select your answer

To handle form submit actions asynchronously.

To trigger a re-render when a value changes.

To persist values across renders without causing a re-render on update.

To memoize computation results for caching purposes.

Question 15/15

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

Select your answer

useState hook

Redux

CSS-in-JS Libraries like Emotion

Context API

Your Results

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Your Answers

Question 1/15

😊 Your answer was correct 🙁 Your answer was incorrect

What does the Provider component in a Redux application do?

Available answers

Injects the Redux store into the React component tree.

Wraps the event handling logic for the application.

Memorizes static props across re-renders.

Connects to external APIs to fetch initial state.

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 2/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is the default behavior of Context in React regarding re-renders?

Available answers

The components using Context never re-render.

It causes re-renders whenever the Provider's value changes.

It causes re-renders depending on the content of the values, not structural change.

It only re-renders the component where the Context is defined.

React's Context API will cause components that are consuming context data to re-render whenever there is a change in the context's Provider value. This default behavior can be optimized using React.memo or memoized selectors when appropriate.

Question 3/15

😊 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 4/15

😊 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

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

Increase the delay between re-renders

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 5/15

😊 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 6/15

😊 Your answer was correct 🙁 Your answer was incorrect

What is the primary purpose of React's useState hook?

const [count, setCount] = useState(0);

Available answers

To manage component state within functional components

To fetch data from a remote server

To handle form submissions in react

To navigate between routes in a React application

The useState hook in React allows you to add state to functional components. It returns an array with the state value and a function to update it. The code snippet

const [count, setCount] = useState(0);

initializes a state variable count with a value of 0.

Question 7/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

A function that has access to the local component state.

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

A function which can modify its arguments or outside variables.

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

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 8/15

😊 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 provide names to variables within render methods.

To establish the context of an application route.

To enable asynchronous data loading.

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 9/15

😊 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 perform side effects in function components.

To optimize component rendering performance.

To initialize state in class 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 10/15

😊 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 11/15

😊 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 12/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

To enable two sibling components to share and sync state.

To enable JSX to be converted to strings.

To add more states directly to child components.

To reduce execution context in large applications.

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 13/15

😊 Your answer was correct 🙁 Your answer was incorrect

What problem does React Context API primarily solve?

Available answers

Global style management

Passing data through a simple component tree without prop drilling

Routing between components

Reducing state updates from asynchronous actions

The React Context API allows you to share values between components without having to explicitly pass props through every level of the tree. This is particularly useful to avoid 'prop drilling' when you have deeply nested components.

Question 14/15

😊 Your answer was correct 🙁 Your answer was incorrect

What does the useRef hook in React primarily serve?

Available answers

To handle form submit actions asynchronously.

To trigger a re-render when a value changes.

To persist values across renders without causing a re-render on update.

To memoize computation results for caching purposes.

The useRef hook in React is used to persist values across renders without triggering a re-render when the value updates. This is particularly useful for accessing DOM elements directly and storing mutable values.

Question 15/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

useState hook

Redux

CSS-in-JS Libraries like Emotion

Context API

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.