Supreme Javascript Test - 63+ MCQs: JavaScript test: Assess Your Knowledge with JavaScript Questions and Answers

1. What does the 'NaN' in JavaScript stand for?

Not a Number

No Available Number

Negative Available Number

Null and Negative

2. How do you write an IF statement in JavaScript?

if (condition) { // code }

if condition: // code

if { // code } condition

condition ? // code : // code

3. What is the purpose of 'Array.prototype.reduce()' in JavaScript?

Reduces an array to a single value

Reverses the elements of an array

Creates a new array with elements passing a test

Sorts the elements of an array

4. What is the result of the expression '2 + 2' in JavaScript?

undefined

5. Which method is used to add a class to an HTML element in JavaScript?

element.addClass()

element.classList.add()

element.addClassList()

element.addStyle()

6. What is the purpose of the 'typeof' operator in JavaScript?

To check the type of a variable

To define a new variable

To create a new object

To concatenate strings

7. How do you create a class in JavaScript?

class MyClass {}

function MyClass() {}

create class MyClass {}

new Class MyClass {}

8. What is the purpose of the 'localStorage' object in JavaScript?

To store data permanently on the user's device

To access the internet

To handle user input

To create animations

9. How do you write a multi-line comment in JavaScript?

/* This is a multi-line comment */

// This is a multi-line comment

# This is a multi-line comment

' This is a multi-line comment

10. Which of the following is a benefit of using JavaScript modules?

Encapsulation

Code Reusability

Dependency Management

All of the above

11. What is the purpose of the 'addEventListener' method in JavaScript?

To remove an event listener

To add a new element to the DOM

To handle user input

To attach an event handler to an element

12. What is the purpose of the 'map' function in JavaScript?

To create a new array with the results of calling a provided function on every element in the array

To filter elements in an array

To reduce the array to a single value

To reverse the elements of an array

13. Which operator is used for strict equality in JavaScript?

===

!==

14. Which method is used to join elements of an array into a string in JavaScript?

join()

concat()

merge()

combine()

15. What is the purpose of 'Array.isArray()' in JavaScript?

Checks if a variable is an array

Adds an element to an array

Removes an element from an array

Sorts the elements of an array

16. Which of the following is a falsy value in JavaScript?

NaN

false

All of the above

17. What is the purpose of 'JSON.stringify()' in JavaScript?

Converts an object to a JSON string

Parses a JSON string

Creates a new JSON object

Deletes a JSON property

18. What is the purpose of the 'async' keyword in JavaScript?

To define a synchronous function

To handle exceptions

To indicate that a function returns a promise

To create an asynchronous loop

19. How do you create an object in JavaScript?

let obj = {}

new Object()

Object.create()

All of the above

20. How do you declare a variable in JavaScript?

v myVar;

var myVar;

variable myVar;

let myVar;

21. Which method is used to remove the last element from an array in JavaScript?

pop()

push()

shift()

unshift()

22. Which of the following is a valid way to declare a JavaScript array?

var myArray = []

array myArray = []

new Array()

myArray = {}

23. What is the purpose of 'Array.prototype.filter()' in JavaScript?

Creates a new array with elements passing a test

Removes elements from an array

Sorts the elements of an array

Reverses the elements of an array

24. What is the result of the expression '2' + 2 in JavaScript?

'22'

'4'

An error

25. How do you create a comment in JavaScript?

// This is a comment

# This is a comment

/* This is a comment */

26. How do you check if an element has a specific class in JavaScript?

element.hasClass()

element.isClass()

element.containsClass()

element.classList.contains()

27. Which function is used to parse a JSON string in JavaScript?

parseJSON

evalJSON

JSON.parse

parseString

28. How do you round the number 7.25 to the nearest integer in JavaScript?

Math.round(7.25)

Math.ceil(7.25)

Math.floor(7.25)

round(7.25)

29. What is the purpose of 'setTimeout()' in JavaScript?

Executes a function after a specified time

Pauses the execution of a function

Adds a delay to CSS animations

Sets an interval for a function

30. Which keyword is used to define a constant in JavaScript?

const

let

var

constant

31. What is the purpose of 'Promise' in JavaScript?

Handles asynchronous operations

Performs mathematical calculations

Creates an array of elements

Defines a function

32. What is the result of the expression '3 * '2' + 1' in JavaScript?

Error

Undefined

33. What does HTML stand for?

Hyper Text Markup Language

Hyperlinks and Text Markup Language

Home Tool Markup Language

Hyper Transfer Markup Language

34. What is the purpose of the 'reduce' method in JavaScript?

To create a new array with the results of calling a provided function on every element in the array

To filter elements in an array

To reduce the array to a single value

To reverse the elements of an array

35. Which statement is used to exit a switch statement in JavaScript?

break

exit

return

end

36. What does CSS stand for?

Counter Style Sheet

Computer Style Sheet

Colorful Style Sheet

Cascading Style Sheet

37. What is the purpose of the 'addEventListener()' method in JavaScript?

Attaches an event handler to an element

Adds a new CSS class

Removes an element from the DOM

Creates a new HTML element

38. How do you declare a function in JavaScript?

function myFunction() { // code }

def myFunction():

create function myFunction():

new_function myFunction():

39. How do you comment a single line in JavaScript?

// This is a comment

/* This is a comment */

# This is a comment

' This is a comment

40. What is a closure in JavaScript?

A way to create private variables

A function that has access to variables in its lexical scope

An object with no properties

A special type of loop

JavaScript MCQ Test 2