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JavaScript Interview Questions Set-1

/25

JAVASCRIPT Interview Question

Prepare for Interview

1 / 25

What is the purpose of the "concat()" method in JavaScript?

To add elements to the beginning of an array

To combine two or more arrays into a single array

To remove elements from an array

To sort the elements of an array

2 / 25

What will be the output of the following code?

const x = "5";

const y = 2;

console.log(x + y);

"52"

"5"+2

3 / 25

How do you check if a variable is undefined in JavaScript?

if (variable === null)

if (variable === undefined)

if (typeof variable === "undefined")

if (isUndefined(variable))

4 / 25

Which method is used to remove the first element from an array in JavaScript?

unshift()

pop()

shift()

removeFirst()

5 / 25

What does the "let" keyword do in JavaScript?

Declares a private variable

Declares a block-scoped variable

Declares a global variable

Declares a constant variable

6 / 25

Which method is used to find the index of the first occurrence of an element in an array?

findIndex()

indexOf()

search()

find()

7 / 25

How do you round a number to the nearest integer in JavaScript?

round()

Math.round()

Math.floor()

ceil()

8 / 25

What is the correct way to comment a single line in JavaScript?

/* This is a comment */

// This is a comment

** This is a comment **

9 / 25

Which method is used to convert a string to an array in JavaScript?

toArray()

split()

toArr()

convertToArray()

10 / 25

What is the purpose of the "splice()" method in JavaScript?

To merge two arrays together

To remove elements from an array and optionally add new elements in their place

To sort the elements of an array

To create a copy of an array

11 / 25

What will be the output of the following code?

"23"

"5"

12 / 25

How do you create a new object in JavaScript using the Object constructor?

const obj = new Object();

const obj = create.Object();

const obj = Object.create();

const obj = createNewObject();

13 / 25

What is the purpose of the "addEventListener" method in JavaScript?

To add comments to the code

To link external CSS files

To attach an event handler function to an HTML element

To execute an asynchronous function

14 / 25

Which method is used to convert a string to lowercase in JavaScript?

lower()

changeCase("lower")

toLowerCase()

15 / 25

How do you access the first element of an array named "myArray" in JavaScript?

myArray[0]

myArray.first()

myArray(1)

myArray.first

16 / 25

What does the "NaN" value represent in JavaScript?

Not a Number

Null and Nothing

Negative and Null

No Available Number

17 / 25

Which operator is used to compare both value and type in JavaScript?

===

!==

18 / 25

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

The current function

The global object

The parent object

The current object

19 / 25

Which method is used to remove the last element from an array in JavaScript?

removeLast()

pop()

deleteLast()

splice()

20 / 25

How can you check if a variable is an array in JavaScript?

isArr()

isArray()

typeofArray()

typeofArray

21 / 25

What is the output of the following code?

const x = 5;
console.log(x++);

NaN

22 / 25

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

insert()

append()

add()

push()

23 / 25

Which keyword is used to declare a variable in JavaScript?

var

int

let

variable

24 / 25

What does the acronym "DOM" stand for in JavaScript?

Document Object Model

Data Object Model

Document Order Model

Data Orientation Mechanism

25 / 25

What is the purpose of the "sort()" method in JavaScript?

To add elements to the end of an array

To combine two or more arrays into a single array

To remove elements from an array

To sort the elements of an array

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JavaScript Interview Questions Set-2

/30

JavaScript Practice Set

Check Your JavaScript Now

1 / 30

What is the purpose of the `async` keyword in a JavaScript function declaration?

To make the function run synchronously

To specify the function's return type

To indicate that the function will perform asynchronous operations

To define a callback function

2 / 30

How do you remove the first element from an array in JavaScript?

By using the removeFirst() method

By using the splice(0, 1) method

By using the shift() method

By using the pop() method

3 / 30

What is the result of `[1, 2, 3] + [4, 5]` in JavaScript?

[1, 2, 3, 4, 5]

"12345"

[1, 2, 3, "4", "5"]

NaN

4 / 30

Which array method creates a new array by applying a function to each element of the original array?

map()

filter()

reduce()

forEach()

5 / 30

What method is used to add elements to the end of an array in JavaScript?

push()

append()

insert()

add()

6 / 30

How do you access the last element of an array in JavaScript?

By using the pop() method

By using the index array[length-1]

By using the shift() method

By using the last() method

7 / 30

What does the `arguments` object represent within a function in JavaScript?

The list of parameters passed to the function

The function's return value

The global scope of the function

The current date and time

8 / 30

What is the result of `typeof function() {}` in JavaScript?

"function"

"object"

"undefined"

"string"

9 / 30

What is the purpose of the `bind()` method in JavaScript?

To create a new function with a specified this value

To concatenate two or more strings

To remove an element from an array

To sort an array in ascending order

10 / 30

What is a callback function in JavaScript?

A function that performs mathematical calculations

A function that is executed immediately upon declaration

A function that is passed as an argument to another function and is executed later

A function that is used to create new objects

11 / 30

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

It defines the function parameters.

It is used to exit a loop.

It specifies the function's name.

It specifies the value to be returned by the function.

12 / 30

Which keyword is used to refer to the current instance of a class in JavaScript?

this

self

current

instance

13 / 30

What is a constructor in JavaScript?

A function used to create an instance of a class

A method used to call other methods in a class

A built-in object in JavaScript

A way to define private properties in a class

14 / 30

In OOP, what is inheritance?

A process by which objects are created from classes

A way to create multiple instances of a class

The ability of a class to inherit properties and methods from another class

A way to hide the internal details of a class

15 / 30

Which keyword is used to create a class in JavaScript?

class

object

constructor

prototype

16 / 30

What is encapsulation in OOP?

The process of inheriting properties from a superclass

The bundling of data and methods that operate on that data into a single unit

The process of creating a new object from an existing object

The ability to access an object's properties directly

17 / 30

In arrow functions, if you have a single statement, do you need curly braces `{}`?

Yes, always

No, never

Only when using if statements

Only when returning an object

18 / 30

Which of the following statements is true about arrow functions?

They are always anonymous.

They cannot have more than one parameter.

They use the function keyword.

They have their own this binding.

19 / 30

Arrow functions do NOT have their own:

this

arguments

scope

return statement

20 / 30

What does the arrow (=>) symbol signify in arrow functions?

Function definition

Function invocation

Function declaration

Function call

21 / 30

Which of the following is a valid arrow function syntax in JavaScript?

function add(a, b) => a + b

(a, b) => { return a + b; }

let add = (a, b) -> a + b

function (a, b) { return a + b; }

22 / 30

Which loop is used for iterating through the properties of an object?

for loop

while loop

do...while loop

for...in loop

23 / 30

What is the purpose of the `parseInt()` function in JavaScript?

To convert a string to an integer

To find the position of a substring

To parse JSON data

To round a floating-point number

24 / 30

Which operator is used for strict equality (both value and type)?

===

!==

25 / 30

How do you declare a constant variable in JavaScript?

const myVar = 10;

let myVar = 10;

var myVar = 10;

constant myVar = 10;

26 / 30

Which function is used to print something to the console in JavaScript?

console.print()

print()

log()

display()

27 / 30

Which keyword is used to declare a variable in JavaScript?

var

int

let

string

28 / 30

How can you comment a single line in JavaScript?

// Comment

/* Comment */

''' Comment '''

29 / 30

Which of the following is not a JavaScript data type?

String

Boolean

Character

Number

30 / 30

What does JavaScript primarily add to a webpage?

Styling

Interactivity

Database connectivity

Animation

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Interview Questions

JavaScript Interview Questions​ Set-1

What is the purpose of the "concat()" method in JavaScript?

What will be the output of the following code?

How do you check if a variable is undefined in JavaScript?

Which method is used to remove the first element from an array in JavaScript?

What does the "let" keyword do in JavaScript?

Which method is used to find the index of the first occurrence of an element in an array?

How do you round a number to the nearest integer in JavaScript?

What is the correct way to comment a single line in JavaScript?

Which method is used to convert a string to an array in JavaScript?

What is the purpose of the "splice()" method in JavaScript?

What will be the output of the following code?

How do you create a new object in JavaScript using the Object constructor?

What is the purpose of the "addEventListener" method in JavaScript?

Which method is used to convert a string to lowercase in JavaScript?

How do you access the first element of an array named "myArray" in JavaScript?

What does the "NaN" value represent in JavaScript?

Which operator is used to compare both value and type in JavaScript?

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

Which method is used to remove the last element from an array in JavaScript?

How can you check if a variable is an array in JavaScript?

What is the output of the following code?

const x = 5; console.log(x++);

What is the purpose of the "sort()" method in JavaScript?

JavaScript Interview Questions​ Set-2

What is the purpose of the async keyword in a JavaScript function declaration?

How do you remove the first element from an array in JavaScript?

What is the result of [1, 2, 3] + [4, 5] in JavaScript?

Which array method creates a new array by applying a function to each element of the original array?

What method is used to add elements to the end of an array in JavaScript?

How do you access the last element of an array in JavaScript?

What does the arguments object represent within a function in JavaScript?

What is the result of typeof function() {} in JavaScript?

What is the purpose of the bind() method in JavaScript?

What is a callback function in JavaScript?

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

Which keyword is used to refer to the current instance of a class in JavaScript?

What is a constructor in JavaScript?

In OOP, what is inheritance?

Which keyword is used to create a class in JavaScript?

What is encapsulation in OOP?

In arrow functions, if you have a single statement, do you need curly braces {}?

Which of the following statements is true about arrow functions?

Arrow functions do NOT have their own:

What does the arrow (=>) symbol signify in arrow functions?

Which of the following is a valid arrow function syntax in JavaScript?

Which loop is used for iterating through the properties of an object?

What is the purpose of the parseInt() function in JavaScript?

Which operator is used for strict equality (both value and type)?

How do you declare a constant variable in JavaScript?

Which function is used to print something to the console in JavaScript?

Which keyword is used to declare a variable in JavaScript?

How can you comment a single line in JavaScript?

Which of the following is not a JavaScript data type?

What does JavaScript primarily add to a webpage?

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JavaScript Interview Questions Set-1

const x = 5;
console.log(x++);

JavaScript Interview Questions Set-2

What is the purpose of the `async` keyword in a JavaScript function declaration?

What is the result of `[1, 2, 3] + [4, 5]` in JavaScript?

What does the `arguments` object represent within a function in JavaScript?

What is the result of `typeof function() {}` in JavaScript?

What is the purpose of the `bind()` method in JavaScript?

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

In arrow functions, if you have a single statement, do you need curly braces `{}`?

What is the purpose of the `parseInt()` function in JavaScript?

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