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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

Memorizes static props across re-renders.

Connects to external APIs to fetch initial state.

Wraps the event handling logic for the application.

Injects the Redux store into the React component tree.

Question 2/15

What mechanism does Redux use to update its state?

Select your answer

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

Components directly mutate the store object.

Reducers compute a new state based on actions dispatched.

Action creators update the global state through context managers.

Question 3/15

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 provide names to variables within render methods.

To enable asynchronous data loading.

Question 4/15

What are selectors in Redux?

Select your answer

UI elements that represent the current state.

Functions to extract and compute derived state from the Redux store.

Functions to dispatch asynchronous actions in Redux.

Methods to connect reducers to actions.

Question 5/15

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

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

Select your answer

To directly mutate the Redux store state.

To update the component styles.

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

To reset the global store to its initial state.

Question 6/15

What problem does React Context API primarily solve?

Select your answer

Reducing state updates from asynchronous actions

Passing data through a simple component tree without prop drilling

Routing between components

Global style management

Question 7/15

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

Select your answer

Asynchronous JavaScript functions can execute during creation.

It uses HTML validation for form inputs.

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

CSS styles are automatically applied to form elements.

Question 8/15

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

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

Select your answer

Every time the component re-renders.

Only once, when the component mounts.

Whenever the 'count' state changes.

Never, because 'useEffect' is not properly configured.

Question 9/15

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 handle form submissions in react

To fetch data from a remote server

To navigate between routes in a React application

Question 10/15

What is React's useEffect hook used for?

Select your answer

To directly update the DOM manually.

To optimize component rendering performance.

To perform side effects in function components.

To initialize state in class components.

Question 11/15

What happens if you call setState inside a useEffect hook without specifying a dependency array?

useEffect(() => { setState('value'); });

Select your answer

The updates happen after the component mounts once.

The setState function will be ignored during renders.

It creates an infinite loop of re-renders.

setState will not be evaluated because it's asynchronous.

Question 12/15

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

Select your answer

Limit the number of state variables

Use

React.memo

to wrap the component

Increase the delay between re-renders

Publish the component in a separate thread

Question 13/15

What does the useRef hook in React primarily serve?

Select your answer

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

To trigger a re-render when a value changes.

To memoize computation results for caching purposes.

To handle form submit actions asynchronously.

Question 14/15

What's the role of the useContext hook?

Select your answer

To dispatch actions in reducers.

To subscribe a component to context changes.

To initialize state in function components.

To perform side-effects in function components.

Question 15/15

When using Redux, what does the 'connect' function primarily do?

Select your answer

Allows asynchronous actions to be dispatched in Redux.

Subscribes a component to Redux store updates and wraps the component with Redux data and actions.

Merges CSS styles in a Redux-connected application.

Provides a higher-order reducer for microservices.

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

Memorizes static props across re-renders.

Connects to external APIs to fetch initial state.

Wraps the event handling logic for the application.

Injects the Redux store into the React component tree.

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 mechanism does Redux use to update its state?

Available answers

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

Components directly mutate the store object.

Reducers compute a new state based on actions dispatched.

Action creators update the global state through context managers.

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 3/15

😊 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 provide names to variables within render methods.

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 4/15

😊 Your answer was correct 🙁 Your answer was incorrect

What are selectors in Redux?

Available answers

UI elements that represent the current state.

Functions to extract and compute derived state from the Redux store.

Functions to dispatch asynchronous actions in Redux.

Methods to connect reducers to actions.

Selectors in Redux are functions used to retrieve specific pieces of the state tree or compute derived state based on the Redux store's current state. They allow components to access store data with encapsulated retrieval logic, keeping the component code cleaner.

Question 5/15

😊 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 directly mutate the Redux store state.

To update the component styles.

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

To reset the global store to its initial state.

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 6/15

😊 Your answer was correct 🙁 Your answer was incorrect

What problem does React Context API primarily solve?

Available answers

Reducing state updates from asynchronous actions

Passing data through a simple component tree without prop drilling

Routing between components

Global style management

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 7/15

😊 Your answer was correct 🙁 Your answer was incorrect

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

Available answers

Asynchronous JavaScript functions can execute during creation.

It uses HTML validation for form inputs.

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

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 8/15

😊 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

Every time the component re-renders.

Only once, when the component mounts.

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.

Question 9/15

😊 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 handle form submissions in react

To fetch data from a remote server

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 10/15

😊 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 perform side effects in function components.

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 11/15

😊 Your answer was correct 🙁 Your answer was incorrect

What happens if you call setState inside a useEffect hook without specifying a dependency array?

useEffect(() => { setState('value'); });

Available answers

The updates happen after the component mounts once.

The setState function will be ignored during renders.

It creates an infinite loop of re-renders.

setState will not be evaluated because it's asynchronous.

Calling setState inside a useEffect hook without a dependency array is a common pitfall leading to an infinite loop. This happens because each call to setState causes a re-render, which in turn triggers the useEffect again immediately.

Question 12/15

😊 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

Limit the number of state variables

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

Increase the delay between re-renders

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 13/15

😊 Your answer was correct 🙁 Your answer was incorrect

What does the useRef hook in React primarily serve?

Available answers

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

To trigger a re-render when a value changes.

To memoize computation results for caching purposes.

To handle form submit actions asynchronously.

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 14/15

😊 Your answer was correct 🙁 Your answer was incorrect

What's the role of the useContext hook?

Available answers

To dispatch actions in reducers.

To subscribe a component to context changes.

To initialize state in function components.

To perform side-effects in function components.

The useContext hook is used to subscribe a function component to a context. It simplifies the retrieval of the current value of a context compared to using a context consumer.

Question 15/15

😊 Your answer was correct 🙁 Your answer was incorrect

When using Redux, what does the 'connect' function primarily do?

Available answers

Allows asynchronous actions to be dispatched in Redux.

Subscribes a component to Redux store updates and wraps the component with Redux data and actions.

Merges CSS styles in a Redux-connected application.

Provides a higher-order reducer for microservices.

The connect function from the React-Redux library is used to connect a React component to the Redux store. It allows you to map state and dispatch actions to props so that the component can subscribe to store updates and send updates.