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

1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

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. 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

9. 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

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

Using refs

Using props

Using state

Using context

11. 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

12. 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

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. 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

15. How can you optimize performance in React?

By using class components

By using Redux

By using the PureComponent class

By using inline styles

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. 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

28. How can you optimize the performance of a React application that renders a large list of items?

By using inline styles for each item

By applying a unique key to each list item

By avoiding the use of the useMemo hook

By using a single state object for all list items

29. How can you conditionally render elements in React?

Using the if statement

Using the switch statement

Using the map function

Using ternary operators

30. What is a React Hook?

A functional component

A reusable piece of logic

A component's lifecycle method

A way to style React components

React MCQ Test 3