Master JavaScript Fundamentals: A Comprehensive Guide for Beginners

Question 1

What primary function does the 'this' keyword serve in JavaScript?

Accepted Answer

To refer to the current object

Answer

To create a new object

Answer

To invoke a function

Answer

To access global variables

Question 2

What is the intended purpose of the 'debugger' statement in JavaScript?

Accepted Answer

To halt execution and enable code inspection

Answer

To print debugging information

Answer

To trigger an error

Answer

To optimize code performance

Question 3

When naming variables in JavaScript, which of the following is considered best practice?

Accepted Answer

Use descriptive and meaningful names

Answer

Commence names with underscores

Answer

Employ brief and ambiguous names

Answer

Utilize reserved keywords

Question 4

Explain the distinction between '==' and '===' in JavaScript.

Accepted Answer

'==' evaluates value equality, while '===' assesses both value and type equality

Answer

'===' evaluates value equality, while '==' assesses both value and type equality

Answer

They are interchangeable and execute the same operation

Answer

They are both logical operators

Question 5

Which data type is specifically used to represent a range of whole numbers?

Accepted Answer

Integer

Answer

Number

Answer

String

Answer

Object

Question 6

What is the primary purpose of using the 'let' keyword?

Accepted Answer

To declare a variable with a limited scope within a block

Answer

To declare a constant variable

Answer

To declare a globally scoped variable

Answer

To declare a function

Question 7

Which operator is used to determine if two values are equal?

Accepted Answer

==

Answer

!=

Answer

>

Answer

<

Question 8

What is the outcome of the expression: 10 % 3?

Accepted Answer

1

Answer

0

Answer

3

Answer

10

Question 9

Which built-in method is used to convert a string to uppercase characters?

Accepted Answer

toUpperCase()

Answer

toLowerCase()

Answer

trim()

Answer

charAt()

Question 10

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

Accepted Answer

To obtain a reference to an HTML element based on its unique ID

Answer

To create a new HTML element

Answer

To remove an HTML element from the DOM

Answer

To add an event listener to an HTML element

Question 11

Which event listener is triggered when the user clicks on an HTML element?

Accepted Answer

onclick

Answer

onload

Answer

onhover

Answer

onsubmit

Question 12

What is the correct syntax for defining a function in JavaScript?

Accepted Answer

function myFunction() {}

Answer

myFunction() {}

Answer

function = myFunction {}

Answer

myFunction = function() {}

Question 13

Which keyword is used to define a class in JavaScript?

Accepted Answer

class

Answer

object

Answer

define

Answer

create

Question 14

What is the primary purpose of the 'this' keyword?

Accepted Answer

To refer to the current object

Answer

To define a global variable

Answer

To pass arguments to a function

Answer

To call a parent method

Question 15

What is the purpose of the '===' operator in JavaScript?

Accepted Answer

To check for strict equality, comparing both value and type

Answer

To check for loose equality, coercing values before comparison

Answer

To compare objects by reference

Answer

To compare arrays by content

Question 16

What is the output of the following code? const message = 'Hello'; message += 'World'; console.log(message);

Accepted Answer

HelloWorld

Answer

Hello

Answer

World

Answer

Error

Question 17

What is the purpose of the 'try...catch' statement in JavaScript?

Accepted Answer

To handle errors and exceptions during program execution

Answer

To create a custom error message

Answer

To prevent the program from crashing

Answer

To debug the program

Question 18

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

Accepted Answer

A 'let' variable can be reassigned, while a 'const' variable cannot

Answer

A 'const' variable can be reassigned, while a 'let' variable cannot

Answer

There is no difference between the two variable types

Answer

A 'let' variable is global, while a 'const' variable is local

Question 19

Which of the following syntax is used to declare a variable in JavaScript?

Accepted Answer

var variableName;

Answer

int variableName;

Answer

const variableName;

Answer

VariableName = 10;

Question 20

What is the data type of the value '10' in JavaScript?

Accepted Answer

Number

Answer

String

Answer

Array

Answer

Boolean

Question 21

Which operator is used for strict equality comparison in JavaScript?

Accepted Answer

===

Answer

=

Answer

!=

Answer

==

Question 22

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

Accepted Answer

To declare a constant variable.

Answer

To declare a global variable.

Answer

To declare an anonymous function.

Answer

To declare a variable with block scope.

Question 23

Which data structure in JavaScript is used to store a collection of key-value pairs?

Accepted Answer

Object

Answer

Array

Answer

List

Answer

Map

Question 24

Which of the following is a valid JavaScript event listener?

Accepted Answer

element.addEventListener('click', myFunction);

Answer

onclick('myFunction');

Answer

on('click', myFunction);

Answer

listen('click', myFunction);

Question 25

What does the 'this' keyword refer to in JavaScript?

Accepted Answer

The current executing object.

Answer

The global object.

Answer

The parent object.

Answer

The child object.

Question 26

Which of the following is a valid JavaScript conditional statement syntax?

Accepted Answer

if (condition) { code } else { code }

Answer

for (condition) { code }

Answer

switch (condition) { case: code }

Answer

while (condition) { code }

Question 27

What is the main difference between 'let' and 'var' variables in JavaScript?

Accepted Answer

Let variables have block scope, while var variables have function or global scope.

Answer

Let variables can only be declared once.

Answer

Let variables are immutable.

Answer

Var variables cannot be used in loops.