1. What is ReactJS?
a) A back-end framework
b) A front-end framework
c) A JavaScript library
d) A web server
Answer: c) A JavaScript library
2. What is virtual DOM in ReactJS?
a) A programming language
b) A virtual machine
c) A virtual database
d) A virtual representation of the DOM (Document Object Model)
Answer: d) A virtual representation of the DOM (Document Object Model)
3. What is JSX in ReactJS?
a) A programming language
b) A file format
c) A visual representation of components
d) A syntax extension for JavaScript
Answer: d) A syntax extension for JavaScript
4. What is the purpose of rendering in ReactJS?
a) To update the DOM with new changes
b) To create a virtual DOM
c) To manage state in a component
d) To store data in memory
Answer: a) To update the DOM with new changes
5. What is the purpose of props in ReactJS?
a) To manage state in a component
b) To pass data from one component to another
c) To create a virtual DOM
d) To display content on a page
Answer: b) To pass data from one component to another
6. What is the difference between state and props in ReactJS?
a) State is used for data that changes frequently, while props are used for data that does not change frequently
b) State is used for data that does not change frequently, while props are used for data that changes frequently
c) State and props are used interchangeably
d) State and props are not used in ReactJS
Answer: a) State is used for data that changes frequently, while props are used for data that does not change frequently
7. What is the purpose of setState() method in ReactJS?
a) To update the state of a component
b) To update the props of a component
c) To create a new component
d) To delete a component
Answer: a) To update the state of a component
8. What is the difference between functional and class components in ReactJS?
a) Functional components are used for styling, while class components are used for logic
b) Functional components use the render() method, while class components have a render() method
c) Functional components do not have state, while class components have state
d) Functional components are not used in ReactJS
Answer: c) Functional components do not have state, while class components have state
9. What is the purpose of componentWillMount() method in ReactJS?
a) To update the state of a component before it renders
b) To update the DOM with new changes
c) To manage state in a component
d) To store data in memory
Answer: a) To update the state of a component before it renders
10. What is the purpose of componentDidUnmount() method in ReactJS?
a) To update the state of a component before it renders
b) To update the DOM with new changes
c) To manage state in a component
d) To perform any necessary cleanup before a component is unmounted
Answer: d) To perform any necessary cleanup before a component is unmounted
11. What is the purpose of shouldComponentUpdate() method in ReactJS?
a) To update the state of a component
b) To update the DOM with new changes
c) To manage state in a component
d) To determine whether a component should be updated or not
Answer: d) To determine whether a component should be updated or not
12. What is the purpose of componentDidCatch() method in ReactJS?
a) To handle errors in a component tree
b) To update the DOM with new changes
c) To manage state in a component
d) To store data in memory
Answer: a) To handle errors in a component tree
13. In ReactJS, what is the purpose of refs?
a) To access the DOM element of a component
b) To access the state of a component
c) To manage props in a component
d) To pass data from one component to another
Answer: a) To access the DOM element of a component
14. What is the purpose of bind() method in ReactJS?
a) To update the state of a component
b) To update the props of a component
c) To bind a method to a component
d) To delete a component
Answer: c) To bind a method to a component
15. What is the purpose of keys in ReactJS?
a) To manage state in a component
b) To pass data from one component to another
c) To identify each component uniquely
d) To store data in memory
Answer: c) To identify each component uniquely
16. What is the purpose of event handling in ReactJS?
a) To change the state of a component
b) To update the props of a component
c) To bind a method to a component
d) To handle user interactions with a component
Answer: d) To handle user interactions with a component
17. What is the purpose of stateless components in ReactJS?
a) To manage state in a component
b) To pass data from one component to another
c) To create a functional component
d) To create a presentational component
Answer: d) To create a presentational component
18. What is higher-order component in ReactJS?
a) A component that is higher up in the component hierarchy
b) A component that wraps around another component to add functionality
c) A component that has multiple levels of nested components
d) A component that is not used in ReactJS
Answer: b) A component that wraps around another component to add functionality
19. What is the purpose of context in ReactJS?
a) To manage state in a component
b) To pass data from one component to another
c) To create a virtual DOM
d) To display content on a page
Answer: b) To pass data from one component to another
20. What is the purpose of render() method in ReactJS?
a) To update the state of a component
b) To update the props of a component
c) To create a virtual DOM
d) To display content on a page
Answer: d) To display content on a page
21. What is the purpose of componentDidMount() method in ReactJS?
a) To update the state of a component after it renders
b) To update the DOM with new changes
c) To manage state in a component
d) To perform any necessary initialization before a component is mounted
Answer: d) To perform any necessary initialization before a component is mounted
22. What is the purpose of componentDidUpdate() method in ReactJS?
a) To update the state of a component after it renders
b) To update the DOM with new changes
c) To manage state in a component
d) To store data in memory
Answer: a) To update the state of a component after it renders
23. What is the purpose of componentWillReceiveProps() method in ReactJS?
a) To update the state of a component before it receives new props
b) To update the DOM with new changes
c) To manage state in a component
d) To store data in memory
Answer: a) To update the state of a component before it receives new props
24. What is the purpose of setState() in ReactJS?
a) To manage state in a component
b) To pass data from one component to another
c) To update the props of a component
d) To create a new component
Answer: a) To manage state in a component
25. What is the purpose of defaultProps in ReactJS?
a) To set default values for props in a component
b) To manage state in a component
c) To pass data from one component to another
d) To display content on a page
Answer: a) To set default values for props in a component
26. What is the purpose of fragments in ReactJS?
a) To manage state in a component
b) To pass data from one component to another
c) To create a virtual DOM
d) To group a list of children without adding extra nodes to the DOM
Answer: d) To group a list of children without adding extra nodes to the DOM
27. What is the purpose of React Router in ReactJS?
a) To manage state in a component
b) To create a virtual DOM
c) To handle routing in a single-page application
d) To display content on a page
Answer: c) To handle routing in a single-page application
28. What is the purpose of Redux in ReactJS?
a) To manage state in a component
b) To create a virtual DOM
c) To handle complex state management in an application
d) To display content on a page
Answer: c) To handle complex state management in an application
29. What is the purpose of the map() method in ReactJS?
a) To manage state in a component
b) To create a virtual DOM
c) To render a list of items
d) To display content on a page
Answer: c) To render a list of items
30. What is the purpose of React.cloneElement() method in ReactJS?
a) To create a new element from an existing React element
b) To manage state in a component
c) To pass data from one component to another
d) To manage props in a component
Answer: a) To create a new element from an existing React element
31. What is the purpose of React.PureComponent in ReactJS?
a) To create a class component in ReactJS
b) To optimize performance of a React component
c) To manage state in a component
d) To pass data from one component to another
Answer: b) To optimize performance of a React component
32. What is the purpose of React.lazy() function in ReactJS?
a) To create a new component in ReactJS
b) To optimize performance by loading a component only when it is needed
c) To manage state in a component
d) To display content on a page
Answer: b) To optimize performance by loading a component only when it is needed
33. What is the purpose of React.memo() function in ReactJS?
a) To create a new component in ReactJS
b) To optimize performance of a functional component by avoiding unnecessary re-renders
c) To manage state in a component
d) To store data in memory
Answer: b) To optimize performance of a functional component by avoiding unnecessary re-renders
34. What is the purpose of shouldComponentUpdate() method in ReactJS?
a) To update the state of a component
b) To update the DOM with new changes
c) To manage state in a component
d) To determine whether a component should be updated or not
Answer: d) To determine whether a component should be updated or not
35. What is the purpose of React.createContext() function in ReactJS?
a) To manage state in a component
b) To pass data from one component to another
c) To create a new component in ReactJS
d) To display content on a page
Answer: b) To pass data from one component to another
36. What is the purpose of useContext() hook in ReactJS?
a) To manage state in a component
b) To pass data from one component to another using context
c) To create a new component in ReactJS
d) To display content on a page
Answer: b) To pass data from one component to another using context
37. What is the purpose of useReducer() hook in ReactJS?
a) To manage state in a component using the reducer pattern
b) To optimize performance of a React component
c) To create a new component in ReactJS
d) To display content on a page
Answer: a) To manage state in a component using the reducer pattern
38. What is the purpose of useMemo() hook in ReactJS?
a) To manage state in a component
b) To optimize performance by memoizing a computed value
c) To create a new component in ReactJS
d) To display content on a page
Answer: b) To optimize performance by memoizing a computed value
39. What is the purpose of useCallback() hook in ReactJS?
a) To manage state in a component
b) To memoize a callback function
c) To create a new component in ReactJS
d) To display content on a page
Answer: b) To memoize a callback function
40. What is the purpose of useEffect() hook in ReactJS?
a) To manage state in a component
b) To optimize performance by running a side-effect only when necessary
c) To create a new component in ReactJS
d) To display content on a page
Answer: b) To optimize performance by running a side-effect only when necessary
41. What is the purpose of useLayoutEffect() hook in ReactJS?
a) To manage state in a component
b) To optimize performance by running a side-effect immediately after rendering
c) To create a new component in ReactJS
d) To display content on a page
Answer: b) To optimize performance by running a side-effect immediately after rendering
42. What is the purpose of useRef() hook in ReactJS?
a) To manage state in a component
b) To create a mutable ref object
c) To create a new component in ReactJS
d) To display content on a page
Answer: b) To create a mutable ref object
43. What is the difference between useReducer() and useState() hooks in ReactJS?
a) useReducer() is used for simple state management, while useState() is used for complex state management
b) useReducer() is used for complex state management, while useState() is used for simple state management
c) useReducer() and useState() are interchangeable
d) useReducer() and useState() are not used in ReactJS
Answer: b) useReducer() is used for complex state management, while useState() is used for simple state management
44. What is the purpose of React.forwardRef() function in ReactJS?
a) To manage state in a component
b) To forward a ref from a parent to a child component
c) To create a new component in ReactJS
d) To display content on a page
Answer: b) To forward a ref from a parent to a child component
45. What is the purpose of React.memo() function in ReactJS?
a) To create a new component in ReactJS
b) To optimize performance of a functional component by avoiding unnecessary re-renders
c) To manage state in a component
d) To store data in memory
Answer: b) To optimize performance of a functional component by avoiding unnecessary re-renders
46. What is the purpose of memoization in ReactJS?
a) To manage state in a component
b) To optimize performance by caching computed values
c) To create a new component in ReactJS
d) To display content on a page
Answer: b) To optimize performance by caching computed values
47. What is the purpose of React.lazy() function in ReactJS?
a) To create a new component in ReactJS
b) To optimize performance by loading a component only when it is needed
c) To manage state in a component
d) To display content on a page
Answer: b) To optimize performance by loading a component only when it is needed
48. What is the purpose of React.memo() function in ReactJS?
a) To create a new component in ReactJS
b) To optimize performance of a functional component by avoiding unnecessary re-renders
c) To manage state in a component
d) To store data in memory
Answer: b) To optimize performance of a functional component by avoiding unnecessary re-renders
49. What is the purpose of React.Fragment in ReactJS?
a) To manage state in a component
b) To pass data from one component to another
c) To create a new component in ReactJS
d) To group a list of children without adding extra nodes to the DOM
Answer: d) To group a list of children without adding extra nodes to the DOM
50. What is the purpose of React.StrictMode in ReactJS?
a) To manage state in a component
b) To optimize performance of a React component
c) To detect potential problems in a React application
d) To display content on a page
Answer: c) To detect potential problems in a React application.
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