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

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

componentDidMount

componentWillMount

componentDidUpdate

componentWillUnmount

2. Explain the purpose of the React Profiler tool and how it can be used for performance optimization.

The React Profiler tool is used to debug React components

The React Profiler tool is used for styling React components

The React Profiler tool helps analyze the rendering performance of components

The React Profiler tool is used for managing global state in React applications

3. 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

4. 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

5. 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

6. How can you conditionally render elements in React?

Using the if statement

Using the switch statement

Using the map function

Using ternary operators

7. 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

8. How can you handle forms in React?

Using the form tag

Using the state object

Using the onSubmit event

Using the submit() method

9. What is the role of the React Router Switch component, and how does it impact route rendering in a React application?

The React Router Switch component is used for handling asynchronous operations

The React Router Switch component is used to define strict coding rules for React components

The React Router Switch component renders the first child that matches the current location

The React Router Switch component is a replacement for the useTransition hook

10. 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

11. What is the significance of the 'key' prop in React lists?

It defines the component's identity

It specifies the component's style

It sets the component's position

It helps React identify which items have changed, are added, or are removed

12. 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

13. What is the significance of the React.memo function, and how can it optimize performance?

React memo is used for styling in React components

React memo allows the creation of reusable components

React memo is a replacement for the shouldComponentUpdate method

React memo prevents unnecessary re-rendering of functional components

14. How can you handle global state management in a React application without using Redux?

By using the useContext hook

By relying solely on component state

By creating a global variable outside the React component tree

By using the useReducer hook

15. 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

16. 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

17. 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

18. 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

19. What is the purpose of the key attribute in React lists?

It uniquely identifies elements in an array

It sets the background color of elements

It defines the order of elements

It is used for styling purposes

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. What are Hooks in React, and why were they introduced?

Hooks are functions that let you use state and lifecycle features in functional components

Hooks are event listeners in React

Hooks are a replacement for class components

Hooks are used for styling in React

28. 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

29. 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

30. 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

31. What is state in React?

A built-in object

A function

An object that stores component data

A global variable

32. 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

33. Explain the concept of code splitting in React and how it can improve application performance.

Code splitting is a method for writing concise React components

Code splitting is a feature of React Lazy

Code splitting is a technique to divide the application code into smaller chunks

Code splitting has no impact on application performance

34. How can you handle conditional rendering in React?

Using the switch statement

Using the if statement

Using ternary operators

Using the map function

35. 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

36. What is the purpose of the useDebugValue hook in React, and how can it be beneficial?

To optimize rendering performance in React

To define strict coding rules for React components

To debug React components during development

To provide custom names for hooks in React DevTools

37. 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

38. What is the purpose of the withRouter HOC in React?

To handle routing

To create higher-order components

To manage component state

To define the component's lifecycle

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

To memoize functions and optimize performance

To manage component state in class components

To create references to DOM elements

To handle context API in functional components

40. 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

React MCQ Test 2