React Js MCQ Online Test

2. React.js was Initially released in ................

• May 29, 2013
• April 29, 2013
• June 29, 2013
• May 29, 2014

3. React.js has Written in ................

• JavaScript
• Python
• Java
• Php

4. ............. is used in React.js to increase performance?

• Virtual DOM
• Original DOM
• Both Original & Virtual DOM
• None of the Above

5. What is Babel?

• A JavaScript transpiler
• A JavaScript interpreter
• A JavaScript Compiler
• None of the above

6. Which of the following command is used to create a react app?

• install -g create-react-app
• npm install create-react-app
• npx create-react-app reactapp
• None of the Above

7. .............. port is the default where the webpack-dev-server will run.

• 3030
• 8080
• 3306
• 3000

8. A valid react component can return only ......... element.

• 2
• 3
• 1
• 4

9. A state in React.js is also known is ..............

• A permanent storage.
• An Internal storage of the component.
• An External storage of the component.
• All of the above

10. In React js what is used to pass data to a component from outside?

• setState
• render with arguments
• props
• PropTypes

11. How can you access the state of a component from inside of a member function?

• this.getState()
• this.values
• this.prototype.stateValue
• this.state

12. Props are __________ into other components.

• Methods
• Injected
• Both 1 & 2
• All of the above

13. What is a react.js in MVC?

• Middleware
• Controller
• Model
• View

14. Keys are given to a list of elements in react. These keys should be -

• Do not requires to be unique
• Unique in the DOM
• Unique among the siblings only
• All of the above

15. Which of the following is the correct data flow sequence of flux concept?

• Dispatcher->Action->Store->View
• Action->Dispatcher->View->Store
• Action->Dispatcher->Store->View
• Action->Store->Dispatcher->View

16. React.js covers only the view layer of the app.

• Yes
• No

17. React was originally developed by ...............

• Jordan Walke
• Rasmus Lerdorf
• Miško Hevery
• None of the above

18. .............. helps react for keeping their data unidirectional.

• JSX
• Flux
• Dom
• Props

19. React merges the object you provide into the current state using setState().

• True
• False

20. Arbitrary inputs of components are called ...........

• Ref
• Keys
• Props
• Elements

21. We can prevent default behavior in React using ............

• revokeDefault()
• preventDefault()
• avoidDefault()
• None of the Above

22. React is mainly used for building ................

• Database
• User interface
• Connectivity
• Design platform

23. What is the smallest building block of ReactJS?

• props
• elements
• components
• None of the Above

24. Which function is used to change the state of react component?

• this.State{}
• this.setState
• this.setChangeState
• None of the Above

25. What is React js?

• client-side framework
• server-side framework
• ui (user interface) framework
• None of the above

26. Which of the following is used to create a class inheritance?

• this
• Create
• Extends
• Inherits

27. What are the ways to handle data in react.js?

• state & services
• state & component
• State & props
• services & component

28. Which of the following method is used for the parent class in React.Js?

• self()
• this()
• Inherits()
• super()

29. React components are saved in ....................... directory.

• js/components
• components/js
• vendor/components
• None of the above

30. useLayoutEffect function is used to .................

• complete the update
• optimize for all devices
• change the layout of the screen
• when we need the browser to paint before effectors