JavaScript Syntax and Structure: Master the Basics of JavaScript

Question 1

In JavaScript, which keyword is used to declare a function?

Accepted Answer

function

Answer

define

Answer

declare

Answer

def

Question 2

Which data type in JavaScript is used to store a sequence of characters?

Accepted Answer

string

Answer

number

Answer

boolean

Answer

array

Question 3

Which control flow statement in JavaScript is used to conditionally execute a block of code?

Accepted Answer

if

Answer

switch

Answer

for

Answer

while

Question 4

In JavaScript, which character is used to terminate a statement?

Accepted Answer

;

Answer

:

Answer

,

Answer

.

Question 5

What is the main purpose of the 'use strict' directive in JavaScript?

Accepted Answer

Enable stricter error checking

Answer

Disable debugging

Answer

Enhance code performance

Answer

Define a namespace

Question 6

Consider the JavaScript code snippet: console.log(null == undefined);. What will be printed as the output?

Accepted Answer

true

Answer

false

Answer

null

Answer

undefined

Question 7

What operator is used to concatenate strings in JavaScript?

Accepted Answer

+

Answer

-

Answer

*

Answer

/

Question 8

Which keyword is used to declare a named function in JavaScript?

Accepted Answer

function

Answer

def

Answer

declare

Answer

create

Question 9

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

Accepted Answer

To declare a constant variable

Answer

To declare a function

Answer

To create an object

Answer

To define an array

Question 10

What is the key difference between single and double quotes in JavaScript string literals?

Accepted Answer

Double quotes escape characters, single quotes do not

Answer

None

Answer

Single quotes escape characters, double quotes do not

Answer

Single quotes can be used to define multi-line strings

Question 11

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

Accepted Answer

===

Answer

==

Answer

!=

Answer

!=

Question 12

Which of the following is not a valid syntax for creating an array in JavaScript?

Accepted Answer

array()

Answer

[]

Answer

new Array()

Answer

Array()

Question 13

Which JavaScript operator checks both the value and the type of two variables?

Accepted Answer

===

Answer

==

Answer

>

Answer

||

Question 14

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

Accepted Answer

object

Answer

string

Answer

number

Answer

boolean

Question 15

Which of the following control flow statements is used to execute a block of code repeatedly until a condition is met?

Accepted Answer

while

Answer

if

Answer

for

Answer

switch

Question 16

Which keyword is used to define a class in JavaScript?

Accepted Answer

class

Answer

define

Answer

create

Answer

declare

Question 17

Which of the following is NOT a valid scope in JavaScript?

Accepted Answer

protected

Answer

global

Answer

local

Answer

block

Question 18

Which of the following data structures is used to store a unique collection of values in JavaScript?

Accepted Answer

set

Answer

array

Answer

object

Answer

map

Question 19

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

Accepted Answer

push

Answer

add

Answer

append

Answer

insert

Question 20

Which of the following event listeners is used to detect when a keyboard key is pressed?

Accepted Answer

onkeydown

Answer

onkeypress

Answer

onkeyup

Answer

oninput

Question 21

Which of the following is NOT a benefit of using JavaScript in web development?

Accepted Answer

Improved security

Answer

Dynamic content

Answer

Enhanced user experience

Answer

Reduced development time

Question 22

In JavaScript, what's the main reason to use a `switch` statement?

Accepted Answer

To run code based on different conditions

Answer

To loop through data

Answer

To create functions

Answer

To handle errors

Question 23

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

Accepted Answer

Character

Answer

Number

Answer

Boolean

Answer

Array

Question 24

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

Accepted Answer

To declare a variable

Answer

To assign a value to a variable

Answer

To create a function

Answer

To compare two variables

Question 25

Which comparison operator is used to check if two values are equal?

Accepted Answer

==

Answer

!=

Answer

>

Answer

<

Question 26

What is the result of executing the following code: console.log(typeof null);

Accepted Answer

object

Answer

null

Answer

undefined

Answer

error

Question 27

Which of the following control flow statements is used to execute a block of code only if a specified condition is satisfied?

Accepted Answer

if

Answer

while

Answer

for

Answer

switch

Question 28

Differentiate between 'let' and 'const' variable declarations.

Accepted Answer

Let variables can be reassigned, while const variables cannot

Answer

Const variables can be reassigned, while let variables cannot

Answer

Both are equivalent to var variables

Answer

There is no difference

Question 29

Predict the output of the following code: var num = 10; num += 5; console.log(num);

Accepted Answer

15

Answer

5

Answer

10

Answer

error

Question 30

In JavaScript, what is the concept of encapsulation?

Accepted Answer

Combining data and methods into objects, concealing internal details

Answer

Inheriting properties and methods from parent classes

Answer

Creating objects with private, public, and protected access levels

Question 31

Which operator is used to check the strict equality of two values in JavaScript?

Accepted Answer

===

Answer

==

Answer

!=

Answer

>

Question 32

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

Accepted Answer

To execute a block of code only if a specified condition is true

Answer

To loop through an array

Answer

To define a function

Answer

To create a new object

Question 33

What is the key difference between a variable and a constant in JavaScript?

Accepted Answer

Variables can be reassigned, while constants cannot be changed

Answer

Constants can be reassigned, while variables cannot be changed

Answer

Variables and constants are interchangeable in JavaScript

Answer

Both variables and constants cannot be changed once assigned

Question 34

Which method is used to convert a numeric value to a string in JavaScript?

Accepted Answer

toString()

Answer

toInt()

Answer

toNumber()

Answer

toStr()

Question 35

What is the primary purpose of the `for` loop in JavaScript?

Accepted Answer

To iterate over a sequence of values or objects

Answer

To define a function

Answer

To create a new object

Answer

To execute a block of code only if a specified condition is true

Question 36

What is the primary role of the `console.log()` method in JavaScript?

Accepted Answer

To display data or messages in the browser console for debugging purposes

Answer

To define a function

Answer

To create a new object

Answer

To execute a block of code

Question 37

Which of the following best describes asynchronous programming in JavaScript?

Accepted Answer

Code runs at the same time, without waiting for previous code to finish.

Answer

Code runs in a sequence, one line at a time.

Answer

Code only runs when a user interacts with the webpage.

Answer

Code only runs when an internet connection is available.

Question 38

How does JavaScript's event-driven model handle events?

Accepted Answer

Events are handled in a separate thread, allowing the main thread to continue running.

Answer

Code execution pauses while events are processed.

Answer

The browser only checks for events when the program asks it to.

Answer

JavaScript processes events one at a time, in order.

Question 39

Which syntax is correct for a try-catch block in JavaScript?

Accepted Answer

try { ... } catch (error) { ... }

Answer

catch { ... } finally { ... }

Answer

try { ... } finally { ... } catch (error) { ... }

Question 40

In JavaScript, what is a primary benefit of inheritance?

Accepted Answer

Sharing methods between objects

Answer

Creating objects with identical properties

Answer

Limiting access to specific properties and methods

Answer

Creating objects that are completely independent

Question 41

Which of the following best describes the purpose of this JavaScript code block?
```
if (x > 10) {
   console.log('x is greater than 10');
}
```

Accepted Answer

Conditional Statement

Answer

Loop Statement

Answer

Array Statement

Question 42

What is a key characteristic of higher-order functions in JavaScript?

Accepted Answer

Can be stored in variables like other values

Answer

Cannot take functions as inputs

Answer

Cannot return functions as outputs

Answer

Must not cause side effects

Question 43

In JavaScript, how do you assign the value 'John Doe' to the variable 'name'?

Accepted Answer

name = 'John Doe'

Answer

var name: 'John Doe'

Answer

const name = 'John Doe'

Answer

name := 'John Doe'

Question 44

Which statement accurately describes asynchronous programming within JavaScript?

Accepted Answer

Asynchronous operations are executed in a separate thread, running параллельно to the main thread.

Answer

Code execution proceeds sequentially, one line at a time.

Answer

Code execution halts until asynchronous operations are completed.

Answer

Asynchronous programming is only feasible in specific JavaScript environments.

Question 45

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

Accepted Answer

+

Answer

/

Answer

*

Answer

-

Question 46

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

Accepted Answer

To execute code only when a certain condition is true

Answer

To iterate through an array

Answer

To define a function

Question 47

What is the main purpose of the 'return' statement in a JavaScript function?

Accepted Answer

To end the function's execution and provide a result

Answer

To iterate through an array

Answer

To specify a function's parameters

Question 48

What is the correct syntax for creating an object in JavaScript?

Accepted Answer

{}

Answer

()

Answer

[]

Answer

<>

Question 49

Which data type in JavaScript is used to represent a sequence of characters?

Accepted Answer

String

Answer

Object

Answer

Number

Answer

Boolean

Question 50

Which operator is used in JavaScript for addition?

Accepted Answer

+

Answer

*

Answer

-

Answer

/

Question 51

Which of the following is NOT a valid variable name in JavaScript?

Accepted Answer

22variable

Answer

_variable

Answer

$variable

Question 52

Which operator is used in JavaScript for strict equality comparison?

Accepted Answer

===

Answer

!=

Answer

<>

Answer

==

Question 53

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

Accepted Answer

if

Answer

switch

Answer

for

Answer

while

Question 54

Which data type in JavaScript represents a true or false value?

Accepted Answer

Boolean

Answer

Object

Answer

String

Answer

Number

Question 55

Which control flow statement in JavaScript is used to repeat a block of code a specific number of times?

Accepted Answer

for

Answer

do-while

Answer

if

Answer

while