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React MCQ

What is React?
- A. A programming language
- B. A JavaScript library for building user interfaces
- C. A CSS preprocessor
- D. A server-side scripting language
Answer: B. A JavaScript library for building user interfaces
What does JSX stand for?
- A. JavaScript XML
- B. JavaScript Extension
- C. JSX doesn't stand for anything
- D. Java XML Syntax
Answer: A. JavaScript XML
Which method is used to render a React element into a DOM element?
- A. renderDOM
- B. mount
- C. renderElement
- D. ReactDOM.render
Answer: D. ReactDOM.render
In React, what is the purpose of setState?
- A. To set the initial state of a component
- B. To update the state of a component
- C. To get the current state of a component
- D. To remove a component from the state
Answer: B. To update the state of a component
What is the Virtual DOM used for in React?
- A. To create a virtual representation of the browser
- B. To store component styles
- C. To improve performance by updating the actual DOM more efficiently
- D. To handle asynchronous events
Answer: C. To improve performance by updating the actual DOM more efficiently

Which lifecycle method is called after a component renders for the first time?
- A. componentWillMount
- B. componentDidMount
- C. componentWillUpdate
- D. componentDidUpdate
Answer: B. componentDidMount
In class components, which method is used to update the state based on props changes?
- A. componentDidMount
- B. componentDidUpdate
- C. componentWillReceiveProps
- D. componentWillUpdate
Answer: C. componentWillReceiveProps

Which hook is used for side effects in functional components?
- A. useEffect
- B. useSideEffect
- C. useAsyncEffect
- D. useLifecycle
Answer: A. useEffect
What is the purpose of the useState hook?
- A. To define state in class components
- B. To fetch data from an API
- C. To manage state in functional components
- D. To create a global state
Answer: C. To manage state in functional components

What is the key difference between state and props in React?
- A. State is used for internal component data, while props are used for communication between components.
- B. State is immutable, while props are mutable.
- C. State is passed down from parent components, while props are defined within a component.
- D. State is used only in class components, while props are used in functional components.
Answer: A. State is used for internal component data, while props are used for communication between components.
In React, how can you pass data from a parent component to a child component?
- A. Using the setState method
- B. Using the props attribute
- C. Using the state attribute
- D. Using the render method
Answer: B. Using the props attribute

What is React Router used for?
- A. State management in React applications
- B. Handling routing and navigation in React applications
- C. Managing API requests
- D. Styling React components
Answer: B. Handling routing and navigation in React applications
Which component is used to define a route in React Router?
- A. Router
- B. Switch
- C. Route
- D. Link
Answer: C. Route

What is Redux used for in a React application?
- A. Styling React components
- B. Managing global state
- C. Handling routing and navigation
- D. Fetching data from an API
Answer: B. Managing global state
What is an action in Redux?
- A. A plain JavaScript object describing a change in state
- B. A function that calculates the next state
- C. A middleware for handling side effects
- D. A component in a Redux application
Answer: A. A plain JavaScript object describing a change in state

What is a Higher-Order Component (HOC) in React?
- A. A component with a higher number of children
- B. A function that takes a component and returns a new component with enhanced features
- C. A component with a higher level of state
- D. A component that renders other components
Answer: B. A function that takes a component and returns a new component with enhanced features

What is React Context used for?
- A. Managing global state
- B. Styling React components
- C. Handling routing and navigation
- D. Creating higher-order components
Answer: A. Managing global state
How can you consume a React Context in a functional component?
- A. Using the this.context property
- B. Using the useContext hook
- C. Using the Consumer component
- D. Using the connect function
Answer: B. Using the useContext hook

What is a React Portal used for?
- A. Handling API requests
- B. Rendering components outside the normal component hierarchy
- C. Managing global state
- D. Animating React components
Answer: B. Rendering components outside the normal component hierarchy

Which testing library is commonly used for testing React components?
- A. Jest
- B. Mocha
- C. Jasmine
- D. Enzyme
Answer: A. Jest

React MCQ