Supreme React Test - 72+ MCQs: React test: Evaluate Your Proficiency with React Questions and Answers

1. What are the advantages of using the Redux library in a React application?

To simplify state management and make it predictable

To eliminate the need for component state

To handle form validation in React

To optimize rendering performance

2. Explain the concept of controlled components in React.

Components that are directly manipulated by the DOM

Components that maintain their own state

Components that rely on Redux for state management

Components that receive props from parent components

3. Which lifecycle method is invoked once, immediately after a component is inserted into the DOM?

componentDidMount

componentWillMount

componentDidUpdate

componentWillUnmount

4. What is the role of the useContext hook in React?

To handle context API

To manage component state

To update the virtual DOM

To define the component's lifecycle

5. What is the role of the useImperativeHandle hook in React, and when should it be used?

To create custom hooks in React

To manage component state in class components

To expose imperative methods to parent components

To define the initial state of a component

6. In React, what is the significance of the useMemo hook?

To memoize functions

To manage component state

To handle side effects

To optimize performance

7. In React, what is the role of the render() method?

To update the component's state

To render JSX elements

To handle user interactions

To define component properties

8. How does the useDeferredValue hook in React contribute to improving performance, and in what scenarios is it beneficial?

The useDeferredValue hook enhances the transition animations in React

The useDeferredValue hook is used for handling routing in React

The useDeferredValue hook improves the performance of asynchronous operations

The useDeferredValue hook delays the update of a value until after a specified timeout

9. What are Higher Order Components (HOCs) in React, and how do they work?

Components with a higher level of complexity

Components that use hooks extensively

Functions that return components with enhanced functionality

Components that follow a specific naming convention

10. What is the role of the useRef hook in React?

To create references to DOM elements

To define component properties

To handle context API

To update the virtual DOM

11. How does React Router improve the navigation experience in a React application?

By providing a built-in state management system

By allowing the use of global variables for navigation

By synchronizing the UI with the URL

By preventing the use of dynamic routes

12. What is the purpose of the Redux library in React applications?

To manage component state

To handle routing

To simplify state management

To style React components

13. Explain the concept of server-side rendering (SSR) in React and its advantages.

SSR is a technique to render React components on the server and send HTML to the client

SSR is used for handling client-side routing in React

SSR is a replacement for the useEffect hook

SSR eliminates the need for component state

14. What is the role of the dangerouslySetInnerHTML prop in React?

To set the component's initial state

To handle context API

To update the virtual DOM

To render HTML content dangerously

15. What are the benefits of using the React.forwardRef function, and in what scenarios is it useful?

React.forwardRef is used to create higher-order components

React.forwardRef is used for styling React components

React.forwardRef is beneficial for optimizing rendering performance

React.forwardRef allows the parent component to interact with a child's DOM node

16. What is the purpose of the componentDidCatch method in React?

To handle errors in a component tree

To define the component's initial state

To manage component lifecycle

To handle asynchronous operations

17. How can you handle events in React?

By using the onClick event

By using the bind method

By using the addEventListener method

By using the onEvent prop

18. What is the purpose of the useEffect hook in React?

To perform side effects in function components

To define the component's initial state

To handle component rendering

To manage component lifecycle

19. Explain the concept of error boundaries in React and how they contribute to a better user experience.

Error boundaries catch errors during component rendering and log them to the console

Error boundaries prevent all errors from being logged

Error boundaries are not applicable in functional components

Error boundaries allow components to continue rendering despite errors

20. What are React Hooks rules, and why is it essential to follow them?

Rules that dictate the naming convention of hooks

Guidelines for using hooks within class components

Guidelines for using hooks within functional components

Rules that define the lifecycle of a hook

21. Explain the purpose of the useReducer hook in React.

To handle routing in React applications

To manage complex state logic in functional components

To define the initial state of a component

To handle asynchronous operations

22. What is the significance of virtual DOM in React?

It speeds up rendering

It allows direct manipulation of the DOM

It improves security

It prevents memory leaks

23. How can you pass data from a parent component to a child component in React?

Using refs

Using props

Using state

Using context

24. How can you handle form validation in React?

By using conditional rendering

By using the validate prop

By incorporating the useValidator hook

By implementing controlled components and validation functions

25. What is the purpose of the key prop in React lists?

It sets the background color of elements

It defines the order of elements

It is used for styling purposes

It uniquely identifies elements in an array

26. How can you handle conditional rendering in React?

Using the switch statement

Using the if statement

Using ternary operators

Using the map function

27. How can you handle forms in React?

Using the form tag

Using the state object

Using the onSubmit event

Using the submit() method

28. What is the purpose of the useLayoutEffect hook in React, and how does it differ from useEffect?

To handle layout changes and synchronously apply effects

To manage component state during layout updates

To define the component's initial state

To handle asynchronous operations in functional components

29. Explain the concept of server components in React and how they differ from traditional components.

Server components are components rendered on the server and sent to the client as HTML

Server components are a replacement for the useEffect hook

Server components are used for handling client-side routing in React

Server components have no impact on rendering performance

30. Explain the concept of render props in React and provide a scenario where they are beneficial.

Render props are functions passed as props that return React elements

Render props are used for component styling

Render props are an alternative to using state in React

Render props are only applicable in class components

31. What are the advantages of using the React Context API over prop drilling, and in what scenarios is it preferable?

The React Context API is more efficient for handling global state

The React Context API is only suitable for class components

The React Context API is less performant than prop drilling

The React Context API is beneficial for passing data through deeply nested components

32. Explain the concept of the React Virtual DOM and its impact on performance.

The Virtual DOM is a physical representation of the DOM

The Virtual DOM improves rendering speed by directly manipulating the actual DOM

The Virtual DOM is an alternative to using state in React

The Virtual DOM allows React to efficiently update only the changed parts of the UI

33. What is the significance of React portals?

To create reusable components

To render content outside the DOM hierarchy of a parent component

To handle routing in React

To manage global state in React applications

34. What is the purpose of the React Context API?

To manage component state

To handle context in functional components

To define the component's lifecycle

To create global variables

35. What is state in React?

A built-in object

A function

An object that stores component data

A global variable

36. What is the purpose of the shouldComponentUpdate method in React?

To check if a component should re-render

To define the component's initial state

To handle component lifecycle

To update the virtual DOM

37. What is the role of the arrow function in React?

To create components

To bind event handlers

To define state

To initialize props

38. Explain the role of the React Router Prompt component and when it should be utilized.

The React Router Prompt component is used for handling asynchronous operations

The React Router Prompt component is used to prompt the user before navigating away

The React Router Prompt component defines the initial state of a component

The React Router Prompt component is used for styling React components

39. What does the term 'props drilling' refer to in React?

Passing data from child to parent components

Passing data through multiple layers of components

Passing data from parent to child components

Passing data using context API

40. What is the role of the useHistory hook in React Router, and how can it be used?

To manipulate the browser's history

To define the initial state of a component

To manage context API in functional components

To handle asynchronous operations in functional components

41. How can you optimize performance in React?

By using class components

By using Redux

By using the PureComponent class

By using inline styles

42. How does React handle prop drilling?

By passing props through multiple components

By avoiding the use of props

By directly modifying parent components

By using Redux for state management

43. What is a React Hook?

A functional component

A reusable piece of logic

A component's lifecycle method

A way to style React components

44. What is the significance of the React Fragment?

It represents a virtual DOM element

It is used to create JSX fragments

It defines the lifecycle of a component

It is a replacement for the div element

45. What is the purpose of the React.StrictMode component, and when should it be used?

To define strict coding rules for React components

To optimize rendering performance in React

To catch common coding mistakes and potential issues early

To handle routing in React applications

46. Explain the role of the useEffect hook in managing side effects in React components.

To create effects that run during component rendering

To handle routing in React

To manage asynchronous operations in functional components

To define the component's initial state

47. Explain the concept of custom hooks in React and provide an example of a scenario where they are useful.

Custom hooks are hooks provided by React for common use cases

Custom hooks are only applicable in class components

Custom hooks are functions that use React hooks and can be shared between components

Custom hooks are a replacement for using state in React

48. How can you update the state based on the previous state in React?

By using the setState() method

By using the getSnapshotBeforeUpdate method

By using the useReducer hook

By passing a function to the setState() method

49. Explain the concept of lazy loading in React and how it can improve performance.

Lazy loading is a method for delaying component rendering

Lazy loading is used to load external libraries in React

Lazy loading is a feature of React Suspense

Lazy loading has no impact on performance

50. What is the purpose of state in React?

To store component properties

To manage component styling

To maintain component history

To manage component data over time

React MCQ Test 1