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

1. 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

2. How do you create a class in JavaScript?

class MyClass {}

function MyClass() {}

create class MyClass {}

new Class MyClass {}

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

Number

Boolean

Undefined

Float

4. 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

5. 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

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

join()

concat()

merge()

combine()

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

toUpperCase()

toUpper()

toUpperCaseCase()

upperCase()

8. 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

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

element.addClass()

element.classList.add()

element.addClassList()

element.addStyle()

10. How do you create an object in JavaScript?

let obj = {}

new Object()

Object.create()

All of the above

11. 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

12. 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

13. What is the purpose of 'localStorage' in JavaScript?

Stores data with no expiration date

Stores data with a short expiration date

Stores session-specific data

Stores data in cookies

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

parseJSON

evalJSON

JSON.parse

parseString

15. What does CSS stand for?

Counter Style Sheet

Computer Style Sheet

Colorful Style Sheet

Cascading Style Sheet

16. How do you declare a variable in JavaScript?

v myVar;

var myVar;

variable myVar;

let myVar;

17. How do you declare a function in JavaScript?

function myFunction() { // code }

def myFunction():

create function myFunction():

new_function myFunction():

18. How do you declare a variable in JavaScript?

let

var

const

all of the above

19. How do you create a comment in JavaScript?

// This is a comment

# This is a comment

/* This is a comment */

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

Generates a random number between 0 and 1

Rounds a number to the nearest integer

Finds the square root of a number

Calculates the cosine of a number

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

innerHTML

textContent

innerText

appendText

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 result of the expression '2 + 2' in JavaScript?

undefined

24. 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

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

Encapsulation

Code Reusability

Dependency Management

All of the above

26. 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

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

To bind an event handler to an element

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

To change the value of 'this' in a function

To filter elements in an array

28. How do you comment in JavaScript?

// This is a comment

# This is a comment

/* This is a comment */

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

Handles asynchronous operations

Performs mathematical calculations

Creates an array of elements

Defines a function

30. What does HTML stand for?

Hyper Text Markup Language

Hyperlinks and Text Markup Language

Home Tool Markup Language

Hyper Transfer Markup Language

31. How do you declare a function in JavaScript?

function: myFunction()

func myFunction()

function myFunction()

def myFunction()

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

NaN

false

All of the above

33. 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

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. 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

36. How do you handle errors in asynchronous JavaScript code?

Using try...catch

Using if...else

Using switch statement

Using for loop

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

break

exit

return

end

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

const

let

var

constant

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

pop()

push()

shift()

unshift()

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

Prints output to the console

Defines a new variable

Creates a loop

Imports a module

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

Error

Undefined

42. Which method is used to add an element to the end of an array in JavaScript?

push()

pop()

shift()

unshift()

43. 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)

44. 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

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

if (condition) { // code }

if condition: // code

if { // code } condition

condition ? // code : // code

46. 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

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

===

!==

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

removeLast()

pop()

deleteLast()

splice()

49. What is the purpose of 'document.getElementById()' in JavaScript?

Selects an HTML element by its id

Applies styles to an element

Creates a new HTML element

Removes an element from the DOM

50. 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

JavaScript MCQ Test 1