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

1. 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

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

join()

concat()

merge()

combine()

3. What is the purpose of the 'fetch' function in JavaScript?

To retrieve data from a server

To delete data from a server

To update data on a server

To send an email

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

var myArray = []

array myArray = []

new Array()

myArray = {}

5. 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)

6. How do you create a class in JavaScript?

class MyClass {}

function MyClass() {}

create class MyClass {}

new Class MyClass {}

7. How do you define a JavaScript class?

class MyClass {}

function MyClass() {}

var MyClass = {};

new Class('MyClass')

8. 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

9. What does the 'typeof' operator do in JavaScript?

Returns the type of a variable

Checks if a variable is defined

Concatenates strings

Compares two values

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

undefined

11. What is the purpose of the 'Math.random()' function in JavaScript?

To generate a random number between 0 and 1

To round a number to the nearest integer

To perform a mathematical operation

To check if a number is even or odd

12. Which method is used to change the content of an HTML element in JavaScript?

innerHTML

textContent

innerText

appendText

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

'22'

'4'

An error

14. What does HTML stand for?

Hyper Text Markup Language

Hyperlinks and Text Markup Language

Home Tool Markup Language

Hyper Transfer Markup Language

15. 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

16. 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

17. 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

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

element.addClass()

element.classList.add()

element.addClassList()

element.addStyle()

19. What does CSS stand for?

Counter Style Sheet

Computer Style Sheet

Colorful Style Sheet

Cascading Style Sheet

20. What is the purpose of 'Array.prototype.map()' in JavaScript?

Applies a function to each element of an array

Adds a new element to an array

Filters elements of an array

Reverses the elements of an array

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

removeLast()

pop()

deleteLast()

splice()

22. 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

23. Which of the following is not a JavaScript data type?

Number

Boolean

Undefined

Float

24. How do you declare a function in JavaScript?

function: myFunction()

func myFunction()

function myFunction()

def myFunction()

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

break

exit

return

end

26. 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

27. What is the purpose of the 'querySelector' method in JavaScript?

To select the first element that matches a specified CSS selector

To modify the structure of an HTML document

To create a new element

To retrieve data from a server

28. 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

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

Prints output to the console

Defines a new variable

Creates a loop

Imports a module

30. How do you create an object in JavaScript?

let obj = {}

new Object()

Object.create()

All of the above

31. 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

32. 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

33. 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

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

NaN

false

All of the above

35. Which operator is used to concatenate strings in JavaScript?

concat

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

Encapsulation

Code Reusability

Dependency Management

All of the above

37. How do you declare a variable in JavaScript?

v myVar;

var myVar;

variable myVar;

let myVar;

38. Which method is used to convert a string to uppercase in JavaScript?

toUpperCase()

toUpper()

toUpperCaseCase()

upperCase()

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

Not a Number

No Available Number

Negative Available Number

Null and Negative

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

Error

Undefined

JavaScript MCQ Test 2