JavaScript for Interactivity: Master the Fundamentals of Web Development

Question 1

Which of the following is an invalid variable declaration in JavaScript?

Accepted Answer

myVar

Answer

var myVar

Answer

let myVar

Answer

const myVar = 10

Question 2

Which of the following is NOT a valid primitive data type in JavaScript?

Accepted Answer

Undefined

Answer

Number

Answer

String

Answer

Boolean

Question 3

Which of the following is **not** a primitive data type in JavaScript?

Accepted Answer

Object

Answer

String

Answer

Boolean

Answer

Number

Question 4

Which of the following is NOT a primitive data type in JavaScript?

Accepted Answer

Array

Answer

Number

Answer

String

Answer

Boolean

Question 5

In JavaScript, what's the difference between innerHTML and innerText? Give examples to explain how they're used.

Accepted Answer

innerHTML changes the HTML content of an element, while innerText gets or changes the text content.

Answer

Both innerHTML and innerText can change the HTML content of an element.

Answer

innerHTML gets the text content of an element, while innerText changes the HTML content.

Question 6

What is the main purpose of the XMLHttpRequest (AJAX) object in web applications?

Accepted Answer

To exchange data asynchronously

Answer

To analyze and display XML data

Answer

To check user input

Answer

To store and handle data in the browser

Question 7

Which JavaScript method is used to retrieve an HTML element by its unique ID attribute?

Accepted Answer

getElementById

Answer

querySelector

Answer

getElementsByTagName

Answer

getElementByClassName

Question 8

In JavaScript, what purpose do Promises primarily serve?

Accepted Answer

Providing a structured approach to managing asynchronous operations, representing their eventual success or failure.

Answer

Persisting data beyond the script's execution, ensuring its accessibility throughout the application.

Answer

Creating custom events that can be programmatically or manually triggered.

Question 9

Which of the following is the correct syntax to create a JavaScript function?

Accepted Answer

function myFunction() {}

Answer

myFunction = function() {}

Answer

myFunction {}

Answer

function myFunction

Question 10

What is the purpose of the 'const' keyword in JavaScript?

Accepted Answer

Declares a constant variable

Answer

Declares a variable with block scope

Answer

Initializes a variable

Answer

Declares a function

Question 11

Which of the following data types represents a decimal number in JavaScript?

Accepted Answer

Number

Answer

String

Answer

Boolean

Answer

Object

Question 12

What is the output of the following JavaScript code? var x = 5; x = x + 1; console.log(x);

Accepted Answer

6

Answer

undefined

Answer

5

Answer

Error

Question 13

What is the difference between '==' and '===' in JavaScript?

Accepted Answer

'===' checks for strict equality, while '==' checks for loose equality.

Answer

Both '===' and '==' check for strict equality.

Answer

'==' checks for strict equality, while '===' checks for loose equality.

Question 14

Which of the following methods is used to remove an element from the end of an array in JavaScript?

Accepted Answer

pop()

Answer

splice()

Answer

push()

Question 15

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

Accepted Answer

Selects an element from the document by its unique ID attribute.

Answer

Adds an element to the document.

Answer

Selects all elements that match a specified CSS selector from the document.

Question 16

Which of the following event listeners is used to detect when the mouse enters an element?

Accepted Answer

onmouseover

Answer

onclick

Answer

onkeypress

Answer

onload

Question 17

What is the purpose of a 'while' loop in JavaScript?

Accepted Answer

Executes a block of code repeatedly as long as a specified condition is true.

Answer

Executes a block of code a specified number of times.

Answer

Executes a block of code once.

Answer

Executes a block of code in reverse order.

Question 18

What is the data type of the following JavaScript expression: typeof(10 + '5')?

Accepted Answer

string

Answer

number

Answer

boolean

Answer

integer

Question 19

Which equality comparison operator in JavaScript returns true if both operands are of the same type and value?

Accepted Answer

===

Answer

==

Answer

!=

Answer

=

Question 20

What is the purpose of the 'this' keyword in JavaScript?

Accepted Answer

Refers to the current object context

Answer

Refers to the window object

Answer

Refers to the global object

Answer

Defines a new object

Question 21

What is the key difference between the innerHTML and innerText properties in JavaScript?

Accepted Answer

innerHTML preserves HTML tags, while innerText only displays the text content.

Answer

They are equivalent properties with the same functionality.

Answer

innerText preserves HTML tags, while innerHTML only displays the text content.

Question 22

Which of the following methods modifies an existing JavaScript array by adding a new element to its end?

Accepted Answer

push()

Answer

concat()

Answer

append()

Answer

add()

Question 23

What is the output of executing the following JavaScript code: let s = 'Hello'; s = s.toUpperCase(); console.log(s);

Accepted Answer

HELLO

Answer

'Hello'

Answer

Error

Answer

hello

Question 24

Which of the following is the correct syntax to create a new object using the Object constructor in JavaScript?

Accepted Answer

new Object()

Answer

createObject()

Answer

makeObject()

Answer

new object

Question 25

What is the primary function of the 'document' object in JavaScript?

Accepted Answer

Provides access to the HTML document and its elements

Answer

Represents the browser window

Answer

Serves as the global object

Question 26

What is the output of the following JavaScript code?
console.log(typeof 0 / 0);

Accepted Answer

NaN (Not a Number)

Answer

0

Answer

infinity

Question 27

What is the purpose of the continue statement in a JavaScript loop?

Accepted Answer

To skip the remaining statements in the current iteration and continue with the next iteration.

Answer

To exit the loop immediately.

Answer

To restart the loop from the beginning.

Answer

To pause the loop temporarily.

Question 28

Which JavaScript method is used to remove an attribute from an HTML element?

Accepted Answer

removeAttribute()

Answer

remove()

Answer

delete()

Answer

detach()

Question 29

What is the main difference between getElementById() and querySelector() methods in JavaScript?

Accepted Answer

getElementById() returns a single element by its unique ID, while querySelector() returns the first matching element for a given CSS selector.

Answer

querySelector() can only be used with CSS classes.

Answer

getElementById() is faster than querySelector().

Question 30

Which JavaScript framework is primarily designed for building real-time applications with a focus on data synchronization?

Accepted Answer

Socket.IO

Answer

React

Answer

AngularJS

Answer

jQuery

Question 31

What is the purpose of using the spread (...) operator in JavaScript?

Accepted Answer

To spread the elements of an array or iterable object into individual elements.

Answer

To reverse the order of an array.

Answer

To create a copy of an array.

Question 32

What is the advantage of using a transpiler in JavaScript development?

Accepted Answer

It allows you to write modern JavaScript code that can be run on older browsers that do not support the latest features.

Answer

It can improve the performance of your JavaScript code.

Answer

It can help you write more secure JavaScript code.

Question 33

Which JavaScript data type represents true or false values?

Accepted Answer

boolean

Answer

integer

Answer

string

Question 34

Which JavaScript operator is used to concatenate two strings?

Accepted Answer

+

Answer

%

Answer

*

Answer

/

Question 35

Which JavaScript control structure is used to execute code repeatedly while a condition is true?

Accepted Answer

while

Answer

for

Answer

if

Answer

switch

Question 36

Which JavaScript method is used to retrieve the HTML element with a specific ID from the DOM?

Accepted Answer

getElementById

Answer

querySelector

Answer

getElementsByClassName

Answer

getElementByTagName

Question 37

Which JavaScript event listener is used to handle clicks on an HTML element?

Accepted Answer

onclick

Answer

onchange

Answer

onfocus

Answer

onhover

Question 38

Which JavaScript function is used to create a new instance of an object?

Accepted Answer

new

Answer

make

Answer

build

Answer

create

Question 39

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

Accepted Answer

pop

Answer

shift

Answer

push

Answer

splice

Question 40

Which JavaScript property is used to access the number of elements in an array?

Accepted Answer

length

Answer

elements

Answer

count

Answer

size

Question 41

Which JavaScript method is used to encode a string for transmission over a network?

Accepted Answer

encodeURIComponent

Answer

decodeURIComponent

Answer

escape

Question 42

Which JavaScript function is used to set a timeout for executing a specific code block?

Accepted Answer

setTimeout

Answer

delay

Answer

waitFor

Answer

setInterval

Question 43

Which data type in JavaScript is used to represent true/false values?

Accepted Answer

Boolean

Answer

Object

Answer

String

Answer

Number

Question 44

Which control flow statement in JavaScript is used to execute a block of code only if a condition is true?

Accepted Answer

if

Answer

for

Answer

while

Answer

switch

Question 45

Which method in JavaScript is used to attach an event listener to an HTML element?

Accepted Answer

addEventListener

Answer

bind

Answer

listen

Answer

attachEvent

Question 46

Which HTML attribute is used to specify the JavaScript code to be executed when an event occurs?

Accepted Answer

onclick

Answer

onload

Answer

onsubmit

Question 47

Which JavaScript object represents the browser's current window?

Accepted Answer

window

Answer

location

Answer

document

Answer

navigator

Question 48

Which method in JavaScript is used to select an element in the DOM by its ID?

Accepted Answer

getElementById

Answer

createElement

Answer

querySelector

Answer

innerHTML

Question 49

Which function in JavaScript is used to set a timer that executes a function after a specified delay?

Accepted Answer

setTimeout

Answer

setInterval

Answer

clearInterval

Answer

clearTimeout

Question 50

Which of the following is NOT a characteristic of JavaScript?

Accepted Answer

Static typing

Answer

Event handling

Answer

Dynamic loading

Answer

Object-oriented programming