Javascript

Question 1

What is the output of ‘typeof null’ in JavaScript?

Answer 1

object

Question 2

True or False: JavaScript is a compiled language.

Answer 2

False

Question 3

Fill in the blank: In JavaScript, _____ are used to define a block of code that can be executed later.

Answer 3

functions

Question 4

What does ‘=== ‘ do in JavaScript?

Answer 4

It checks for both value and type equality.

Question 5

What are JavaScript closures?

Answer 5

Functions that have access to the outer function’s scope even after the outer function has returned.

Question 6

Which method is used to convert a JSON string into a JavaScript object?

Answer 6

JSON.parse()

Question 7

What will the following code output: console.log(0.1 + 0.2 === 0.3)?

Answer 7

False

Question 8

What is the purpose of the ‘this’ keyword in JavaScript?

Answer 8

It refers to the object that is currently executing the function.

Question 9

True or False: JavaScript supports multiple inheritance.

Answer 9

False

Question 10

What is a promise in JavaScript?

Answer 10

An object that represents the eventual completion or failure of an asynchronous operation.

Question 11

Which symbol is used to create an object in JavaScript?

Answer 11

{}

Question 12

What will be the output of the following code: console.log(typeof NaN)?

Answer 12

number

Question 13

Fill in the blank: JavaScript is primarily used for _____ in web development.

Answer 13

client-side scripting

Question 14

What does the ‘map’ method do in JavaScript?

Answer 14

It creates a new array populated with the results of calling a provided function on every element in the calling array.

Question 15

What is the difference between ‘let’ and ‘var’ in JavaScript?

Answer 15

‘let’ has block scope, while ‘var’ has function scope.

Question 16

What are template literals in JavaScript?

Answer 16

String literals allowing embedded expressions, enclosed by backticks (``).

Question 17

What is the use of ‘async’ and ‘await’ in JavaScript?

Answer 17

They are used to work with asynchronous code, making it easier to read and write.

Question 18

Which operator is used to destructure an array in JavaScript?

Answer 18

[ ]

Question 19

What is the output of ‘[] + []’ in JavaScript?

Question 20

True or False: Arrow functions do not have their own ‘this’ context.

Answer 20

True

Question 21

What is the purpose of the ‘bind’ method in JavaScript?

Answer 21

It creates a new function that, when called, has its ‘this’ keyword set to the provided value.

Question 22

What will the following code output: console.log(‘5’ - 2)?

Answer 22

3

Question 23

What is event delegation in JavaScript?

Answer 23

A technique that allows you to attach a single event listener to a parent element to manage events for multiple child elements.

Question 24

Fill in the blank: In JavaScript, _____ are variables that can hold multiple values.

Answer 24

arrays

Question 25

What is the purpose of the 'reduce' method in JavaScript?

Answer 25

It executes a reducer function on each element of the array, resulting in a single output value.

Question 26

What does 'JSON.stringify()' do in JavaScript?

Answer 26

It converts a JavaScript object or value to a JSON string.

Question 27

Which keyword is used to declare a constant in JavaScript?

Answer 27

const