React State Management Quiz

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Question 1/15

What does the Provider component in a Redux application do?

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Question 2/15

What mechanism does Redux use to update its state?

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Question 3/15

Why should keys be unique among siblings in React?

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Question 4/15

What are selectors in Redux?

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Question 5/15

Consider the following Redux action. What is its primary purpose?
const fetchData = () => ({ type: 'FETCH_DATA' });

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Question 6/15

What problem does React Context API primarily solve?

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Question 7/15

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

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Question 8/15

Consider the following use of useEffect. When does the effect run?
useEffect(() => { console.log('Updated!'); }, [count]);

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Question 9/15

What is the primary purpose of React's useState hook?
const [count, setCount] = useState(0);

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Question 10/15

What is React's useEffect hook used for?

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Question 11/15

What happens if you call setState inside a useEffect hook without specifying a dependency array?
useEffect(() => { setState('value'); });

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Question 12/15

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

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Question 13/15

What does the useRef hook in React primarily serve?

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Question 14/15

What's the role of the useContext hook?

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Question 15/15

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

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Question 1/15
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What does the Provider component in a Redux application do?

Available answers

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
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What mechanism does Redux use to update its state?

Available answers

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
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Why should keys be unique among siblings in React?

Available answers

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
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What are selectors in Redux?

Available answers

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
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Consider the following Redux action. What is its primary purpose?
const fetchData = () => ({ type: 'FETCH_DATA' });

Available answers

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
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What problem does React Context API primarily solve?

Available answers

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

Available answers

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
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Consider the following use of useEffect. When does the effect run?
useEffect(() => { console.log('Updated!'); }, [count]);

Available answers

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
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What is the primary purpose of React's useState hook?
const [count, setCount] = useState(0);

Available answers

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
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What is React's useEffect hook used for?

Available answers

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
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What happens if you call setState inside a useEffect hook without specifying a dependency array?
useEffect(() => { setState('value'); });

Available answers

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

Available answers

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
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What does the useRef hook in React primarily serve?

Available answers

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
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What's the role of the useContext hook?

Available answers

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

Available answers

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.