Master JavaScript: Interactive Web Programming for Beginners

Question 1

In JavaScript, which syntax is correct to declare a variable using the 'var' keyword?

Accepted Answer

var myVariable;

Answer

let myVariable =

Answer

myVariable = 'value';

Answer

const myVariable: string;

Question 2

In JavaScript, which of these is NOT a primitive data type?

Accepted Answer

Object

Answer

Number

Answer

String

Answer

Boolean

Question 3

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

Accepted Answer

Object

Answer

Number

Answer

String

Answer

Boolean

Question 4

The 'var' keyword in JavaScript is primarily used for:

Accepted Answer

Declaring variables

Answer

Handling events

Answer

Defining objects

Answer

Creating functions

Question 5

Which operator is used for logical OR in JavaScript?

Accepted Answer

||

Answer

===

Answer

!=

Answer

&&

Question 6

Which control flow statement is used to execute a block of code as long as a specified condition remains true in JavaScript?

Accepted Answer

while

Answer

do...while

Answer

switch

Answer

for...of

Question 7

The 'document.getElementById()' function in JavaScript is used to:

Accepted Answer

Retrieve an HTML element by its unique ID

Answer

Create a new HTML element

Answer

Add event listeners to an HTML element

Answer

Modify the style of an HTML element

Question 8

Which of the following is **NOT** an advantage of using JavaScript?

Accepted Answer

Enhanced security

Answer

Improved user experience

Answer

Dynamic and interactive web pages

Answer

Cross-platform compatibility

Question 9

The 'this' keyword in JavaScript refers to:

Accepted Answer

The current object within the context of the code it is being used

Answer

A new object created specifically for the 'this' keyword

Answer

The window object

Answer

A global variable accessible throughout the script

Question 10

Which of the following is the correct syntax to declare a variable using the 'let' keyword in JavaScript?

Accepted Answer

let variableName;

Answer

global variableName;

Answer

const variableName;

Answer

var variableName:

Question 11

Which data type is appropriate for representing a numerical value that may contain decimal places?

Accepted Answer

Number

Answer

String

Answer

Array

Answer

Boolean

Question 12

What is the output displayed in the console when the following JavaScript code is executed? 
console.log(typeof NaN);

Accepted Answer

"number"

Answer

"string"

Answer

"boolean"

Answer

"undefined"

Question 13

What is the primary function of the 'this' keyword in JavaScript?

Accepted Answer

It refers to the current object within a method or function.

Answer

It serves to restrict the creation of new objects.

Answer

It's used exclusively for passing arguments to functions.

Answer

It refers to the global object.

Question 14

Which of the following is a key advantage of using JavaScript for web development?

Accepted Answer

Enhanced interactivity and dynamic user experiences.

Answer

Exceptional performance and scalability for demanding applications.

Answer

Minimal learning curve for novice programmers.

Answer

Robust data encryption and security features.

Question 15

What is the purpose of the Document Object Model (DOM) in JavaScript?

Accepted Answer

It represents the HTML document structure as a hierarchical tree of objects.

Answer

It provides a set of functions for working with XML documents.

Answer

It's a tool primarily used for debugging JavaScript code.

Question 16

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

Accepted Answer

addEventListener

Answer

attachEvent

Answer

listen

Answer

bind

Question 17

What is the primary distinction between 'const' and 'let' variable declarations in JavaScript?

Accepted Answer

Variables declared with 'const' are immutable, while those declared with 'let' can be reassigned.

Answer

Variables declared with 'const' are block-scoped, while those declared with 'let' are function-scoped.

Answer

Variables declared with 'const' are hoisted, while those declared with 'let' are not.

Question 18

Which JavaScript data type is designed to store textual information?

Accepted Answer

String

Answer

Object

Answer

Boolean

Answer

Integer

Question 19

In JavaScript, what is the primary purpose of the 'let' keyword?

Accepted Answer

Declares a block-scoped variable

Answer

Declares a constant variable

Answer

Defines a new object

Answer

Declares a function-scoped variable

Question 20

Which of the following is NOT a valid JavaScript logical operator?

Accepted Answer

AND

Answer

!

Answer

&&

Answer

||

Question 21

What is the expected output of the following JavaScript code snippet: 
console.log(typeof NaN);

Accepted Answer

number

Answer

NaN

Answer

boolean

Answer

undefined

Question 22

Which of the following is the correct syntax to define a function in JavaScript using arrow function notation?

Accepted Answer

const functionName = () => {}

Answer

() functionName => {}

Answer

function functionName => () {}

Question 23

In JavaScript, what is the primary purpose of the 'bind()' method?

Accepted Answer

Creates a new function with a predefined 'this' value.

Answer

Defines a new object

Answer

Calls a function with specific arguments

Answer

Declares a new scope

Question 24

Which of the following JavaScript code snippets will execute last?

Accepted Answer

setTimeout(() => { console.log('Hello'); }, 1000);

Answer

console.log('World');

Answer

const message = 'Hello World';

Question 25

What is the result of the following JavaScript expression: 10 % 3 ?

Accepted Answer

1

Answer

0

Answer

3

Answer

10

Question 26

Which of the following is a valid way to traverse the DOM (Document Object Model) in JavaScript?

Accepted Answer

document.querySelector('selector');

Answer

document.select('selector');

Answer

document.getElement('selector');

Answer

document.find('selector');

Question 27

What is the difference between 'null' and 'undefined' in JavaScript?

Accepted Answer

'null' is an intentionally assigned value, while 'undefined' is an unassigned value.

Answer

'undefined' is a falsy value, while 'null' is a truthy value.

Answer

'null' can be reassigned, while 'undefined' cannot.

Question 28

Which operator in JavaScript is used for assignment?

Accepted Answer

=

Answer

-=

Answer

==

Answer

+=

Question 29

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

Accepted Answer

123start

Answer

$result

Answer

my_variable

Answer

foo$bar

Question 30

What is the primary purpose of the event loop in JavaScript?

Accepted Answer

To handle asynchronous events without blocking the main thread.

Answer

To manage memory allocation for JavaScript objects.

Answer

To execute JavaScript code in a linear fashion.

Question 31

Which of the following is a popular JavaScript framework that utilizes a component-based architecture?

Accepted Answer

React

Answer

Bootstrap

Answer

Git

Answer

jQuery

Question 32

What is the key difference between the '==' and '===' equality operators in JavaScript?

Accepted Answer

'==' checks for value equality, while '===' checks for both value and type equality.

Answer

'==' is used for assignment, while '===' is used for comparison.

Answer

'==' is case-sensitive, while '===' is not.

Question 33

Which of the following is NOT a built-in method of the Array object in JavaScript?

Accepted Answer

sortNumbers

Answer

join

Answer

push

Answer

pop

Question 34

What operator is used to concatenate two strings in JavaScript?

Accepted Answer

+

Answer

&

Answer

~

Answer

*

Question 35

Which control flow statement is used to execute a block of code only if a certain condition is met?

Accepted Answer

if

Answer

while

Answer

switch

Answer

until

Question 36

What is the purpose of the 'document' object in JavaScript?

Accepted Answer

To represent and interact with the HTML document

Answer

To create new HTML elements

Answer

To handle user input

Answer

To perform calculations

Question 37

Which function is used to add an event listener to an HTML element?

Accepted Answer

addEventListener

Answer

trigger

Answer

on

Answer

attachEvent

Question 38

What is the key difference between a 'let' and 'const' variable in JavaScript?

Accepted Answer

Let variables can be reassigned, while const variables cannot

Answer

Let variables are block-scoped, while const variables are globally scoped

Answer

Const variables can be reassigned, while let variables cannot

Question 39

Which method is used to convert a JavaScript object to a JSON string?

Accepted Answer

JSON.stringify()

Answer

object.toJSON()

Answer

JSON.parse()

Question 40

What is the purpose of the 'prototype' property in JavaScript?

Accepted Answer

To inherit properties and methods from other objects

Answer

To store the object's type

Answer

To access the object's constructor function

Question 41

Which JavaScript method is used to create a new array containing a copy of a specified range of elements from an existing array?

Accepted Answer

slice()

Answer

concat()

Answer

map()

Answer

splice()

Question 42

What is the main difference between a 'function declaration' and a 'function expression' in JavaScript?

Accepted Answer

Function declarations are hoisted, while function expressions are not

Answer

Function declarations can be anonymous, while function expressions cannot

Answer

Function expressions can be reassigned, while function declarations cannot

Question 43

In JavaScript, which operator is used to test equality of values?

Accepted Answer

==

Answer

!==

Answer

<

Answer

<=

Question 44

What will be the output of the following code snippet? `console.log((5 + 3) * (2 - 1))`

Accepted Answer

8

Answer

10

Answer

5

Answer

Error

Question 45

In JavaScript, which data type is suitable for representing text?

Accepted Answer

string

Answer

float

Answer

int

Answer

boolean

Question 46

What is the primary purpose of the `if` statement in JavaScript?

Accepted Answer

To conditionally execute code based on a given condition.

Answer

To loop through an array.

Answer

To define a function.

Question 47

Which of the following is NOT a reserved keyword in JavaScript?

Accepted Answer

code

Answer

function

Answer

var

Question 48

Explain the distinction between the `==` and `===` comparison operators in JavaScript.

Accepted Answer

`==` checks for value equality, while `===` checks for both value and type equality.

Answer

They are interchangeable in all cases.

Answer

`===` checks for value equality, while `==` checks for both value and type equality.

Question 49

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

Accepted Answer

push

Answer

append

Answer

add

Answer

insert

Question 50

What is the outcome of the code snippet? `let x = 1; x++`

Accepted Answer

2

Answer

Error

Answer

x

Answer

1

Question 51

In JavaScript, which function is an example of an asynchronous function?

Accepted Answer

fetch()

Answer

Math.sqrt()

Answer

console.log()

Question 52

What is the purpose of a callback function in JavaScript?

Accepted Answer

To pass data or invoke a function when an asynchronous operation completes.

Answer

To create a new object.

Answer

To define a reusable function.