JavaScript Basics: A Comprehensive Guide for Beginners

Question 1

Which of the following data types is used to represent positive and negative numbers?

Accepted Answer

Number

Answer

String

Answer

Boolean

Answer

Array

Question 2

Which of the following operators is used to assign a value to a variable?

Accepted Answer

=

Answer

+=

Answer

-=

Answer

/=

Question 3

What is the purpose of the "const" keyword?

Accepted Answer

To declare a constant variable

Answer

To define a function

Answer

To create an object

Answer

To import a module

Question 4

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

Accepted Answer

variable

Answer

for

Answer

while

Answer

const

Question 5

What is the output of the following code snippet? var a = 10; a += 5;

Accepted Answer

15

Answer

5

Answer

10

Answer

Error

Question 6

What is the purpose of the "debugger" keyword?

Accepted Answer

To pause execution of the code

Answer

To print the stack trace

Answer

To create a new breakpoint

Answer

To log a message to the console

Question 7

What is the difference between the "==" and "===" operators?

Accepted Answer

== checks for value equality, === checks for value and type equality

Answer

=== checks for value equality, == checks for value and type equality

Answer

They are the same operator

Answer

== is used for numbers, === is used for strings

Question 8

Which JavaScript code correctly declares a variable?

Accepted Answer

let myVar = 10;

Answer

int myVar;

Answer

const myVar;

Answer

var myVar: number;

Question 9

Which data type is utilized to represent values of true or false?

Accepted Answer

Boolean

Answer

Number

Answer

String

Answer

Array

Question 10

What operator is used to join strings together?

Accepted Answer

+

Answer

*

Answer

/

Answer

%

Question 11

What is the function of the `if` statement?

Accepted Answer

To execute code based on a condition

Answer

To iterate over a loop

Answer

To define a function

Answer

To handle errors

Question 12

Which event listener is utilized to respond to user interactions?

Accepted Answer

click

Answer

load

Answer

resize

Answer

scroll

Question 13

Which method is used to select elements by their class name?

Accepted Answer

getElementsByClassName

Answer

getElementById

Answer

querySelector

Answer

querySelectorAll

Question 14

What is the purpose of a regular expression?

Accepted Answer

All the above.

Answer

To validate user input

Answer

To find and replace text

Answer

To analyze complex data structures

Question 15

In JavaScript, how does hoisting impact the execution of this code snippet?

```javascript
console.log(x);
var x = 10;
```

Accepted Answer

It moves the declaration of `x` to the top of the scope, making it accessible before its assignment.

Answer

It allows access to the variable `x` before it is declared and assigned.

Answer

It assigns the value of `10` to `x` before the console statement.

Answer

It has no effect on the execution of the code.

Question 16

What is the main purpose of using the 'for...in' loop in JavaScript?

Accepted Answer

Iterate through the properties (keys) of an object

Answer

Iterate through the elements of an array

Answer

Iterate over the values associated with the properties of an object

Answer

Iterate through the methods of an object

Question 17

In JavaScript, which characteristic enables variables to store different data types at various points during program execution?

Accepted Answer

Dynamic Typing

Answer

Static Typing

Answer

Implicit Typing

Question 18

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

Accepted Answer

To declare a variable

Answer

To assign a value to a variable

Answer

To create an object

Answer

To define a function

Question 19

Which of the following operators is used to compare two values for equality in JavaScript?

Accepted Answer

==

Answer

=

Answer

!=

Answer

>

Question 20

What is the output of the following JavaScript code: console.log(10 % 3);

Accepted Answer

1

Answer

0

Answer

3

Answer

10

Question 21

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

Accepted Answer

doWhile

Answer

if

Answer

else

Answer

while

Question 22

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

Accepted Answer

To retrieve an element from the HTML document based on its unique ID

Answer

To create a new element in the HTML document

Answer

To modify the CSS style of an element

Answer

To remove an element from the HTML document

Question 23

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

Accepted Answer

List

Answer

Number

Answer

String

Answer

Boolean

Question 24

What is the main purpose of a variable declaration statement in JavaScript?

Accepted Answer

To establish a new variable and optionally assign a value to it

Answer

To reassign a value to an existing variable

Answer

To retrieve the current value of a variable

Answer

To check the data type of a variable

Question 25

Which operator is used in JavaScript to concatenate two or more strings?

Accepted Answer

+

Answer

-

Answer

*

Answer

/

Question 26

What would be the output of the following JavaScript statement: console.log(typeof 10);

Accepted Answer

'number'

Answer

10

Answer

'string'

Answer

'boolean'

Question 27

What is the distinction between single-line and multi-line comments in JavaScript?

Accepted Answer

Single-line comments start with '//' and end at the end of the line, while multi-line comments start with '/*' and end with '*/

Answer

Multi-line comments start with '//' and end at the end of the line, while single-line comments start with '/*' and end with '*/

Answer

There is no difference between single-line and multi-line comments

Answer

Single-line comments end with '*/', while multi-line comments end with '//'

Question 28

What is the primary goal of using 'strict mode' in JavaScript?

Accepted Answer

To implement stricter rules and prevent potential errors

Answer

To enhance the execution speed of JavaScript code

Answer

To introduce new features and syntax not available in regular mode

Answer

To disable specific JavaScript features

Question 29

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

Accepted Answer

public

Answer

let

Answer

const

Answer

super

Question 30

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

Accepted Answer

To refer to the current object

Answer

To create a new object

Answer

To access properties of the global object

Answer

To declare a new variable

Question 31

Which of the following is the correct syntax to declare and assign value to a variable in JavaScript?

Accepted Answer

let myVariable = 'Value';

Answer

var myVariable;

Answer

const myVariable;

Answer

declare myVariable = value;

Question 32

What is the data type of the variable 'myNumber' in the following code snippet? 
 let myNumber = 10;

Accepted Answer

Number

Answer

String

Answer

Boolean

Answer

Undefined

Question 33

Which of the following operators is used for string concatenation?

Accepted Answer

+

Answer

++

Answer

&

Answer

||

Question 34

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

Accepted Answer

To execute code only if a certain condition is met

Answer

To define a variable

Answer

To iterate through an array

Answer

To handle errors

Question 35

Which of the following methods is used to add an element to the end of an array?

Accepted Answer

push()

Answer

pop()

Answer

shift()

Answer

unshift()

Question 36

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

Accepted Answer

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

Answer

== checks for type equality, while === checks for value equality

Answer

There is no difference between these operators

Answer

== is used for object comparison, while === is used for primitive value comparison

Question 37

Which of the following is NOT a valid JavaScript event handler?

Accepted Answer

onmouseenter

Answer

onclick

Answer

onload

Answer

onchange

Question 38

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

Accepted Answer

To select a single HTML element that matches a specified CSS selector

Answer

To select all HTML elements that match a given CSS selector

Answer

To create a new HTML element

Answer

To modify the CSS style of an HTML element

Question 39

Consider the following code snippet: 
 `var myArray = [1, 2, 3];` 
 `myArray.map((x) => x * 2);` 
 What will be the output of this code?

Accepted Answer

[2, 4, 6]

Answer

Error: map() is not a function

Answer

[1, 2, 3]

Answer

Cannot determine the output

Question 40

In JavaScript, which data type is specifically used to represent floating-point numbers?

Accepted Answer

Number

Answer

String

Answer

Boolean

Question 41

Which operator in JavaScript is used to concatenate strings?

Accepted Answer

+

Answer

/

Answer

-

Answer

*

Question 42

When declaring a variable in JavaScript, which keyword is used to create a variable with a global scope?

Accepted Answer

var

Answer

global

Answer

let

Answer

const

Question 43

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

Accepted Answer

push()

Answer

pop()

Answer

unshift()

Answer

shift()

Question 44

Which of the following represents the correct syntax for defining a function in JavaScript?

Accepted Answer

function myFunction() {}

Answer

myFunction()

Answer

function() { ... }

Answer

myFunction: function() {}

Question 45

In JavaScript, which type of event is triggered when a user clicks on an HTML element?

Accepted Answer

click

Answer

load

Answer

keydown

Answer

change

Question 46

In JavaScript, which method can be used to retrieve the value of a cookie?

Accepted Answer

document.cookie

Answer

getCookie()

Answer

document.getElementById('cookie')

Answer

cookie.getValue()

Question 47

Which of the following is NOT a valid type of JavaScript object?

Accepted Answer

String

Answer

Array

Answer

Object

Answer

Function

Question 48

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

Accepted Answer

Declares a block-scoped variable

Answer

Declares a global variable

Answer

Declares a function

Answer

Declares a constant variable

Question 49

Which operator is used to assign a value to a variable in JavaScript?

Accepted Answer

=

Answer

+

Answer

*

Question 50

What is the correct syntax to declare a variable in JavaScript?

Accepted Answer

let myVariable;

Answer

variable myVariable;

Answer

v myVariable;

Answer

int myVariable;

Question 51

Which of the following data types is used to store whole numbers in JavaScript?

Accepted Answer

Number

Answer

String

Answer

Object

Answer

Boolean

Question 52

What will be the output of the following code?

console.log(typeof "Hello World!");

Accepted Answer

string

Answer

number

Answer

boolean

Question 53

What does the '+' operator do when used with strings in JavaScript?

Accepted Answer

Concatenates the strings.

Answer

Divides the strings.

Answer

Adds the strings as numbers.

Answer

Subtracts the strings.

Question 54

Which keyword is used to declare a constant variable in JavaScript?

Accepted Answer

const

Answer

constant

Answer

var

Answer

let

Question 55

What will be the value of 'result' after executing the following code?

let x = 5;
let result = x++ + ++x;

Accepted Answer

12

Answer

10

Answer

13

Answer

11

Question 56

Which of the following is NOT a valid way to comment in JavaScript?

Accepted Answer

<< This is a comment >>

Answer

// This is a comment

Answer

/* This is a
multiline comment */

Answer

/* This is a comment */

Question 57

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

Accepted Answer

Displays output to the browser's console.

Answer

Writes data to a file.

Answer

Reads input from the user.

Answer

Creates an alert box with a message.

Question 58

What will the following code snippet return?

Boolean(0);

Accepted Answer

false

Answer

undefined

Answer

0

Answer

true

Question 59

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

Accepted Answer

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

Answer

There is no difference, both operators perform the same function.

Answer

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