JavaScript Fundamentals: Master the Basics of Web Development

Question 1

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

Accepted Answer

Array

Answer

Number

Answer

String

Answer

Boolean

Question 2

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

Accepted Answer

if

Answer

for

Answer

while

Answer

switch

Question 3

What is the primary purpose of the 'addEventListener' method in JavaScript?

Accepted Answer

To register an event handler for a particular event

Answer

To generate a new event

Answer

To remove an existing event handler

Answer

To determine if an event has occurred

Question 4

Which operator is NOT a valid mathematical operator in JavaScript?

Accepted Answer

=

Answer

+

Answer

-

Answer

%

Question 5

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

Accepted Answer

To declare a constant that cannot be reassigned

Answer

To declare a variable with global scope

Answer

To declare a variable that can be reassigned

Answer

To declare a local variable

Question 6

What is the main purpose of control flow statements in JavaScript?

Accepted Answer

Control the order in which code is executed

Answer

Store data

Answer

Handle user input

Answer

Change the structure of a web page

Question 7

What is the syntax to add an event listener to an HTML element?

Accepted Answer

element.addEventListener('event', callback);

Answer

element.addEvent('event', callback);

Answer

element.listen('event', callback);

Question 8

Which of the following is a main purpose of the JavaScript document.querySelector() method?

Accepted Answer

To select and modify an HTML element

Answer

To store data in the browser

Answer

To trigger an event on an HTML element

Question 9

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

Accepted Answer

'Let' variables can be reassigned, 'const' variables cannot

Answer

'Const' variables can be reassigned, 'let' variables cannot

Answer

There is no difference between 'let' and 'const' variables

Question 10

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

Accepted Answer

To refer to the current object

Answer

To refer to the global object

Answer

To refer to the parent object

Question 11

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

Accepted Answer

To show output on browser's console

Answer

To gather user's input

Answer

To trigger user's events

Answer

To store data within a database

Question 12

Describe the function of 'this' keyword in JavaScript. When should it be used?

Accepted Answer

References to the current context of the object

Answer

Accesses global variables

Answer

Only applicable in event handling

Answer

Not used in JavaScript

Question 13

Describe the purpose of 'getElementById()' function in JavaScript.

Accepted Answer

To select an HTML element through its ID

Answer

To create a new HTML element

Answer

To modify the content of an HTML element

Answer

To handle user input

Question 14

Which JavaScript loop is employed to iterate through elements of an array?

Accepted Answer

for

Answer

while

Answer

do-while

Answer

foreach

Question 15

What is a key characteristic of primitive data types in JavaScript?

Accepted Answer

They store their values directly, making them immutable.

Answer

They can reference complex data structures like arrays or objects.

Answer

They are always allocated in the heap memory.

Answer

They cannot be passed by reference.

Question 16

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

Accepted Answer

Refers to the current object

Answer

Refers to the global object

Answer

Refers to the parent object

Answer

Refers to the child object

Question 17

Which keyword in JavaScript initiates a conditional statement?

Accepted Answer

if

Answer

switch

Answer

for

Answer

while

Question 18

What is the distinction between the '==' and '===' operators in JavaScript?

Accepted Answer

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

Answer

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

Answer

Both operators have the same functionality

Answer

There is no difference between these operators

Question 19

Which JavaScript event listener is triggered when the user clicks the left mouse button on an element?

Accepted Answer

onclick

Answer

onmouseclick

Answer

onmousedown

Answer

onmouseup

Question 20

What is the primary function of the 'debugger' statement in JavaScript?

Accepted Answer

Pauses execution and opens the debugger tool

Answer

Prints a message to the console

Answer

Throws an error

Answer

Has no effect on the code

Question 21

Which JavaScript function is used to retrieve an element by its unique ID?

Accepted Answer

getElementById

Answer

getElementByClass

Answer

getElementByName

Answer

getElementByTag

Question 22

Which of the following methods is used to add an event listener to an element in JavaScript?

Accepted Answer

addEventListener

Answer

removeEventListener

Answer

triggerEvent

Answer

handleEvent

Question 23

In JavaScript, which method allows you to attach an event listener to an HTML element to respond when the mouse is clicked?

Accepted Answer

addEventListener()

Answer

getEvent()

Answer

onmouseclick()

Answer

click()

Question 24

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

Accepted Answer

if

Answer

while

Answer

for

Answer

switch

Question 25

What is the purpose of the `event` object in JavaScript?

Accepted Answer

To store information about user interactions with web elements

Answer

To handle errors

Answer

To create new elements in the DOM

Answer

To modify CSS styles

Question 26

Which of the following is NOT a valid event listener in JavaScript?

Accepted Answer

onhover

Answer

onclick

Answer

onload

Answer

onchange

Question 27

Which data type in JavaScript is most appropriate for storing numerical values, including those with decimal points?

Accepted Answer

Number

Answer

Boolean

Answer

String

Question 28

Consider the JavaScript code snippet:  
if (x > 5) { 
  console.log('Greater than 5'); 
}. 
What will be the output if x is equal to 4?

Accepted Answer

No output

Answer

'Greater than 5'

Answer

4

Answer

Greater than 5

Question 29

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

Accepted Answer

To refer to the current object

Answer

To declare a new variable

Answer

To invoke a function

Answer

To return the result of the previous expression

Question 30

Which of the following is NOT a valid JavaScript operator?

Accepted Answer

&

Answer

&&

Answer

+

Answer

*

Question 31

Consider the JavaScript code snippet: 
let x = 5; 
x += 3; 
What will be the value of x after this code has run?

Accepted Answer

8

Answer

53

Answer

15

Answer

3

Question 32

Consider the JavaScript code snippet: 
document.getElementById('myElement').style.color = 'red';
What is the purpose of this code?

Accepted Answer

To change the color of the HTML element with the ID 'myElement' to red.

Answer

To create a new HTML element with the ID 'myElement'.

Answer

To retrieve the value of the 'style' attribute of the HTML element with the ID 'myElement'.

Question 33

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

Accepted Answer

To execute blocks of code based on a given condition.

Answer

To monitor user interactions

Answer

To define functions

Answer

To iterate through elements of an array

Question 34

Which event listener in JavaScript is used to respond specifically to user button clicks?

Accepted Answer

onclick

Answer

onkeydown

Answer

onhover

Answer

onchange

Question 35

What is the intended function of the 'break' statement?

Accepted Answer

To terminate execution of a loop or switch statement.

Answer

To continue execution of a loop.

Answer

To skip the upcoming iteration of a loop.

Answer

To halt execution of a loop temporarily.

Question 36

Which event handler is triggered when a user clicks on an element?

Accepted Answer

onclick

Answer

onload

Answer

onsubmit

Answer

onhover

Question 37

In JavaScript, which data type is utilized to represent numeric values?

Accepted Answer

number

Answer

array

Answer

string

Answer

boolean

Question 38

What is the function of the 'if-else' statement in JavaScript?

Accepted Answer

To control the flow of execution based on a given condition.

Answer

To iterate through a sequence of elements.

Answer

To create a reusable function.

Question 39

Which event listener in JavaScript is used specifically for detecting user clicks on an element?

Accepted Answer

addEventListener('click')

Answer

addEventListener('load')

Answer

addEventListener('hover')

Question 40

When executing the following JavaScript code: console.log(typeof null);, what output is produced?

Accepted Answer

object

Answer

string

Answer

number

Question 41

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

Accepted Answer

'==' performs type coercion, while '===' performs strict equality check.

Answer

There is no difference between '==' and '==='.

Answer

'==' is used for assigning values, while '===' is used for comparison.

Question 42

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

Accepted Answer

To refer to the current object.

Answer

To access the global object.

Answer

To create a new object.

Question 43

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

Accepted Answer

Array

Answer

Number

Answer

Boolean

Answer

String

Question 44

Which data type represents integer values in JavaScript?

Accepted Answer

Number

Answer

Object

Answer

Boolean

Answer

String

Question 45

Which control flow statement in JavaScript executes a block of code only when a specified condition is true?

Accepted Answer

if

Answer

switch

Answer

while

Answer

for

Question 46

In JavaScript, which method is used to attach an event listener to an HTML element?

Accepted Answer

addEventListener

Answer

listen

Answer

attachEvent

Answer

on

Question 47

What is the main purpose of a JavaScript object?

Accepted Answer

To store related data and functions as a single entity.

Answer

To handle user input and events.

Answer

To define the structure of a web page.

Question 48

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

Accepted Answer

object

Answer

number

Answer

string

Answer

boolean

Question 49

What is the purpose of the DOM in JavaScript?

Accepted Answer

To represent the structure of a web page.

Answer

To handle network requests.

Answer

To store user preferences.

Answer

To perform complex calculations.

Question 50

Which of the following is a best practice when writing JavaScript code?

Accepted Answer

Use descriptive variable names.

Answer

Write code in a single line.

Answer

Avoid using comments.