ReactJS Multiple-Choice Questions (MCQs) Solved 2024

ReactJS Multiple-Choice Questions (MCQs)

React / ReactJS is a free and open-source front-end JavaScript library for building user interfaces based on UI components. It is maintained by Meta and a community of individual developers and companies. React can be used as a base in the development of single-page or mobile applications.

ReactJS MCQs: This section contains ReactJS Multiple-Choice Questions with Answers. These ReactJS MCQs are written for beginners as well as advanced, practice these MCQs to enhance and test the knowledge of ReactJS.

List of ReactJS MCQs

1. React is also known as _____.

ReactJS
js
Both A. and B.
None of these

Answer: C) Both A. and B.

Explanation:

React is also known as React.js and ReactJS.

2. React is a ____.

Web development Framework
JavaScript Library
jQuery
Web Server

Answer: B) JavaScript Library

Explanation:

React is a JavaScript library.

3. Which ReactJS function renders HTML to the web page?

render()
ReactDOM.render()
renders()
ReactDOM.renders()

Answer: B) ReactDOM.render()

Explanation:

The ReactDOM.render() function is used to render HTML to the web page.

4. JSX stands for _____.

JSON
JSON XML
JavaScript XML
JavaScript and AngularJS

Answer: C) JavaScript XML

Explanation:

JSX stands for JavaScript XML.

5. JSX allows us to write _____.

jQuery in React
Angular Code in React
MySQL in React
HTML in React

Answer: D) HTML in React

Explanation:

JSX allows us to write HTML in React.

6. What is the correct syntax to write expression in JSX?

[ expression ]
{ expression }
{{ expression }}
_expression

Answer: B) { expression }

Explanation:

With JSX, an expression can be written using the syntax, { expression }.

7. A class component must include the _______ statement.

extends React.Component
extends React
extends Component
extends React.Component.All

Answer: A) extends React.Component

Explanation:

A class component must include the extends React.Component statement.

8. What are Props?

Props are arguments passed into React components
Props are functions in the ReactJS
Props are used to returns multiple values from the function
All of the above

Answer: A) Props are arguments passed into React components

Explanation:

Props are arguments passed into React components.

9. What does props stand for?

Proper Arguments
Properties
Proper Return Values
All of the above

Answer: B) Properties

Explanation:

The props stands for properties.

10. Which ReactJS command is used to create a new application?

create-react-app
new-react-app
create-new-reactapp
react-app

Answer: A) create-react-app

Explanation:

The create-react-app command is used to create a new React Application.

11. Which ReactJS command is used to set up everything you need to run a React Application?

create-react-app
new-react-app
create-new-reactapp
react-app

Answer: A) create-react-app

Explanation:

The create-react-app command is used to set up everything you need to run a React Application.

12. How to install create-react-app?

npx create-react-app -new my-app
npx create-react-app -app my-app
npx new-react-app my-app
npx create-react-app my-app

Answer: D) npx create-react-app my-app

Explanation:

The npx create-react-app my-app command is used to install create-react-app.

13. ES6 stands for ____.

ECMAScript 6
Extended-JavaScript Version 6
Extensive-JavaScript 6
Expanded-JavaScript 6

Answer: A) ECMAScript 6

Explanation:

ES6 stands for ECMAScript 6.

14. ECMAScript was created to standardize _____.

TypeScript
Java
JSON
JavaScript

Answer: D) JavaScript

Explanation:

ECMAScript was created to standardize JavaScript.

15. In ES6 – A class is a type of ____.

Basic datatype
Derived datatype
Variable
Function

Answer: D) Function

Explanation:

In ES6 – A class is a type of function.

16. In ES6 – Which keyword is used to initiate a class?

function
class
ReactClass
ReactClassJs

Answer: B) class

Explanation:

In ES6 – A class is a type of function, but instead of using the keyword function to initiate it, we use the keyword class.

17. In ES6 – The class properties are assigned inside a _____ method.

props()
properties()
constructor()
react-properties()

Answer: C) constructor()

Explanation:

In ES6 – The class properties are assigned inside a constructor() method.

class Laptop{

constructor(name) {

this.model = name;

}

18. In ES6 – Which keyword is used for class inheritance?

extends
extend
inheritance
inheritances

Answer: A) extends

Explanation:

In ES6 – The extends keyword is used for class inheritance.

19. In ES6 – What is the correct syntax of class inheritance?

class class1 extends class2{…}
class class1 extends | class2{…}
class class1 | extends class2{…}
class class1 | extends | class2{…}

Answer: A) class class1 extends class2{…}

Explanation:

In ES6 – The correct syntax of class inheritance is:

class class1 extends class2{…}

20. In ES6 – Which method refers to the parent class?

parent()
super()
top()
main()

Answer: B) super()

Explanation:

In ES6 – The super() method refers to the parent class.

21. In ES6 – Why arrow functions are used?

To access pointer variable
To access variable of a class
Both A. and B.
Write shorter function syntax

Answer: D) Write shorter function syntax

Explanation:

In ES6 – The arrow functions are used to write shorter function syntax.

22. Consider the below function – which is the correct syntax of arrow function?

Msg = function() {

return “Good Morning”;

}

Msg = () => {return “Good Morning”;}
Msg = () => “Good Morning”;
Both A. and B.
None of the above

Answer: C) Both A. and B.

Explanation:

In ES6 – Below given both of the syntaxes are correct of arow function:

Msg = () => {

return “Good Morning”;

}

Msg = () => “Good Morning”;

23. Which is the correct arrow function to add two numbers?

add = (a,b) => a+b;
add = (a,b) => return a+b;
add = (a,b) => { return a+b;}
Both A. and B.
Both A. and C.

Answer: E) Both A. and C.

Explanation:

In ES6 – Below given both are the arrow functions to add two numbers:

add = (a,b) => a+b;

add = (a,b) => { return a+b;}

24. With an arrow function – this keyword represents _____.

Content
Header object
Current object
Child object

Answer: B) Header object

Explanation:

With an arrow function – this keyword represents Header object.

25. Complete the below given arrow function.

Msg = ____ “Hi, there!”;

()
=>
()>
() =>

Answer: D) () =>

Explanation:

The correct arrow function is:

Msg = () => “Hi, there!”;

26. In ES6 – Which are the keywords to define variables?

var
let
const
All of the above

Answer: D) All of the above

Explanation:

In ES6 – There are three ways of defining your variables: var, let, and const.

27. In ES6 – var has a function scope, not a block scope?

True
False

Answer: A) True

Explanation:

In ES6 – The statement “var has a function scope, not a block scope.” is True.

28. Which is used to pass data to components from outside?

Render with arguments
props
setState
PropTypes

Answer: B) props

Explanation:

props are used to pass data to components from outside.

29. In ES6 – let is the block scoped version of ____.

const
function
var
None of the above

Answer: C) var

Explanation:

In ES6 – The let is the block scoped version of var.

30. In ES6 – let has a block scope.

True
False

Answer: A) True

Explanation:

In ES6 – The statement “let has a block scope.” is True.

31. In ES6 – Which keyword is used to define a constant?

var
const
let
constant

Answer: B) const

Explanation:

In ES6 – The const keyword is used to define a constant.

32. Which method is used to generate lists?

map()
generate()
new()
maps()

Answer: A) map()

Explanation:

The map() method is used to generate lists in React ES6.

33. What is the default port where webpack-server runs?

443
3030
3306
8080

Answer: D) 8080

Explanation:

The default port to run webpack-server is 8080.

34. What are components in ReactJS?

Components are like functions that return HTML elements.
Components are the HTML elements.
Components are the set of variables defined in ReactJS.
None of the above

Answer: A) Components are like functions that return HTML elements.

Explanation:

In ReactJS, the components are like functions that return HTML elements.

35. How many types of the components in ReactJS?

Answer: B) 2

Explanation:

There are two types of components in ReactJS.

36. Which are the valid components in ReactJS?

Variable components
Function components
Class components
Both A. and B.
Both B. and C.

Answer: E) Both B. and C.

Explanation:

There are two types of components in ReactJS, which are:

Function components
Class components

37. Which statement is required to define a class component?

extends React.Components
imports React.Components
extends React.Component
imports React.Component

Answer: C) extends React.Component

Explanation:

In ReactJS, a class component must include the extends React.Component statement.

38. Consider the below statement – Which method will be used at the place of blank space (____)?

class MainTitle extends React.Component {

______ {

return <h1>Welcome at IncludeHelp!</h1>;

}

renderDOM()
renderComponent()
render()
render()

Answer: C) render()

Explanation:

The correct code is:

class MainTitle extends React.Component {

render() {

return <h1>Welcome at IncludeHelp!</h1>;

}

39. Can components be passed as props?

Answer: A) Yes

Explanation:

Yes, the components can be passed as props.

40. In ReactJS, what is State?

It’s a temporary storage of the elements
It’s a state of the execution of the ReactJS application
It’s an internal storage of the components
All of the above

Answer: C) It’s an internal storage of the components

Explanation:

In ReactJS, the State is an internal storage of the components.

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