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What is a pure component in React?

A component with no side effects
A component that only re-renders when its props change
A component that always re-renders
A component that fetches data

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How do you unmount a component in React?

Using componentWillUnmount
Using componentDidMount
Using useEffect
Using setState

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What is the purpose of keys in React?

To identify elements uniquely
To set state
To define props
To handle events

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What is the purpose of memo in React?

To memoize functions
To prevent unnecessary re-renders
To handle state
To fetch data

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What hook is used to manage state in a functional component?

useContext
useEffect
useReducer
useState

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What is React.js?

A programming language
A JavaScript library for building user interfaces
A database management system
An operating systemAnswer

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What is the purpose of middleware in Redux?

To handle asynchronous actions
To handle synchronous actions
To fetch data
To manage state

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Which of the following is NOT a valid way to style components in React?

Inline styles
External CSS files
Styled-components library
Internal style tags

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What is the purpose of state in React?

To store props
To store component metadata
To manage component input
To manage component data that may change

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How do you handle events in React?

Using addEventListener
Using on prefix in JSX
Using handleEvent method
Using event method

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In React, what does the virtual DOM do?

It directly manipulates the real DOM
It optimizes CSS styling
It provides a way to manipulate browser cookies
It reconciles the changes made to the UI

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Which of the following is NOT a valid lifecycle method in React?

componentWillMount()
componentWillUpdate()
componentDidReceiveProps()
componentWillUnmount

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Which of the following is NOT a built-in Hook in React?

useCallback
useMemo
useState
useComponent

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How do you share state between components?

Using props
Using state
Using context
Using events

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How do you connect a React component to the Redux store?

Using connect
Using useState
Using useEffect
Using useContext

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In React, what is the purpose of keys in arrays of elements?

To uniquely identify each element in the array
To provide styling information
To store component data
To specify element hierarchy

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Which of the following Hooks can be used to subscribe to document title changes in React?

useEffect
useMemo
useContext
useDocumentTitle

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What is the purpose of the 'ref' attribute in React?

To reference external JavaScript files
To create a reference to a DOM element or a React component
To define component dependencies
To specify component props

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How do you lazy load components in React?

Using React.lazy
Using useEffect
Using useContext
Using useState

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In React, what is the purpose of the 'static getDerivedStateFromError' method?

To update the component's state based on errors
To initialize the component's state
To perform cleanup after an error occurs
To handle errors that occur during rendering

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What is the purpose of the 'componentWillReceiveProps' method in React?

To update the component's props
To initialize the component's state
To perform cleanup before the component is removed
To handle errors during rendering

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Who developed React.js?

Google
Apple
Facebook
Microsoft

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What is Redux used for?

State management
Routing
CSS styling
API calls

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Which of the following statements about React Suspense is true?

It is used to handle errors in React components
It is used to suspend rendering while waiting for data to load
It is deprecated in the latest version of React
It is used to manage component state

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What is the purpose of the 'key' prop in React lists?

To specify the index of each item in the list
To uniquely identify each item in the list
To provide styling information for list items
To define the initial state of list items

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How can you prevent a component from re-rendering in React?

By using shouldComponentUpdate method
By returning false from the render method
By setting the 'shouldUpdate' attribute to false
By removing the component from the component tree

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In React, what is the purpose of the 'shouldComponentUpdate' method?

To determine if a component should be rendered
To define component lifecycle
To handle component events
To manage component input

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What is the purpose of useCallback hook?

To memoize functions
To memoize values
To handle side effects
To fetch data

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Which of the following is NOT a valid way to define a component in React?

Function Component
Class Component
Component Component
Higher-Order Component

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What is the purpose of the 'key' prop in React?

It specifies the CSS class of an element
It provides a unique identifier for a component in an array
It defines the initial state of a component
It sets the default props of a component

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