React Js Online Test

1. What happens when the state of a React component changes?

The component re-renders The component becomes unresponsive The component is deleted The component state becomes immutable

2. What is the term used to describe React's ability to update only changed parts of the user interface?

Efficient Rendering Dynamic Reconciliation Virtual DOM Component Reusability

3. What is the purpose of a "deployment pipeline" in React application deployment?

To automate the deployment process To design the user interface To manage database connections To improve code quality

4. What does the term "mocking" refer to in React testing?

Simulating the behavior of dependencies Creating fake components Running tests concurrently Generating random test data

5. What is the primary purpose of the render method in a React component?

To fetch data from an API To render the component's UI To clean up resources when unmounting To update component state

6. In React, what is the purpose of the else block when using conditional rendering?

To define styles for components To conditionally render content To set state in components To create a new component

7. How can you nest error boundaries in a React application?

By using the try-catch statement By wrapping error boundaries around components By using the catch prop in components By creating separate error boundary components

8. What is the primary difference between class components and functional components in React?

Class components use lifecycle methods Functional components use hooks Class components have better performance Functional components cannot accept props

9. How does serverless integration benefit React applications?

It allows for scalable, cost-effective hosting It speeds up component rendering It adds authentication functionality It optimizes code splitting

10. How do you deploy a serverless React application to AWS Lambda?

Using a deployment script Manually copying files to Lambda Creating a Docker container Running a local development server

11. What is the purpose of the required attribute in a React input element?

To set the input value as required To validate the input on submission To disable user input To hide the input field

12. In React, what is the purpose of the index parameter in the map method when rendering a list of items?

To set the item's content To access the previous item in the list To uniquely identify each item To add styling to the item

13. What happens if you omit the else block in a conditional rendering statement in React?

It results in a syntax error The component will not render any content The component will always render The component will throw an error

14. Which built-in Hook is used for performing side effects in a functional component?

useEffect useState useRender useLifecycle

15. What is the primary function of React Router in a React application?

To handle server requests To create reusable UI components To manage client-side routing To manage API requests

16. In React, what is the recommended approach for handling errors when making API requests?

By using try-catch blocks By using inline comments By ignoring errors By using external error handling libraries

17. Which JavaScript library is often used in conjunction with React for state management?

Redux jQuery Lodash Express

18. What is the main principle behind "unidirectional data flow" in React state management?

Data flows from components to a central store Data flows from the central store to components Data flows in multiple directions Data flows only in functional components

19. What is the purpose of the <Link> component in React Router?

To create a hyperlink To define a new route To render a component To manage state in a route

20. Which lifecycle method should be used to perform cleanup when a component is unmounted?

componentDidMount componentWillUnmount componentWillMount render