JavaScript MCQ Questions with answers and solutions Page 146

Q. Which method is used to handle errors in Promises?

(A) catch()
(B) then()
(C) error()
(D) fail()

💬 Discuss

✅ Correct Answer: (A) catch()

Explanation: catch() handles Promise rejections or errors.

Published by Mr. Dubey ⭐ 111.42K Points at 11-Jun-2025 07:19 am in JavaScript

Q. What is the purpose of async keyword in JavaScript?

(A) To define a function that returns a Promise
(B) To pause code execution
(C) To define synchronous code
(D) To create event loops

💬 Discuss

✅ Correct Answer: (A) To define a function that returns a Promise

Explanation: An async function always returns a Promise.

Published by Mr. Dubey ⭐ 111.42K Points at 11-Jun-2025 07:19 am in JavaScript

Q. What is the purpose of the await keyword?

(A) To wait for a Promise to resolve
(B) To block the main thread
(C) To delay function execution
(D) To create a loop

💬 Discuss

✅ Correct Answer: (A) To wait for a Promise to resolve

Explanation: await pauses execution until the Promise resolves or rejects.

Published by Mr. Dubey ⭐ 111.42K Points at 11-Jun-2025 07:19 am in JavaScript

Q. Which JavaScript feature allows function to access variables from an outer scope?

(A) Closure
(B) Scope chain
(C) Callback
(D) Hoisting

💬 Discuss

✅ Correct Answer: (A) Closure

Explanation: Closures give functions access to variables from their outer lexical scope.

Published by Mr. Dubey ⭐ 111.42K Points at 11-Jun-2025 07:19 am in JavaScript

Q. Which keyword is used to define a class in JavaScript?

(A) class
(B) object
(C) structure
(D) function

💬 Discuss

✅ Correct Answer: (A) class

Explanation: The class keyword is used to define a class in ES6+.

Published by Mr. Dubey ⭐ 111.42K Points at 11-Jun-2025 07:19 am in JavaScript

Q. How do you create an instance of a class?

(A) new ClassName()
(B) create ClassName()
(C) object ClassName()
(D) instanceof ClassName()

💬 Discuss

✅ Correct Answer: (A) new ClassName()

Explanation: Use the new keyword to create an instance of a class.

Published by Mr. Dubey ⭐ 111.42K Points at 11-Jun-2025 07:19 am in JavaScript

Q. Which method is automatically called when a new object is created?

(A) constructor
(B) init
(C) create
(D) build

💬 Discuss

✅ Correct Answer: (A) constructor

Explanation: The constructor() method is automatically invoked when an instance is created.

Published by Mr. Dubey ⭐ 111.42K Points at 11-Jun-2025 07:19 am in JavaScript

Q. What is lexical scope?

(A) Scope determined at compile time based on code structure
(B) Scope determined at runtime
(C) Scope of a function inside a loop
(D) Scope within a class

💬 Discuss

✅ Correct Answer: (A) Scope determined at compile time based on code structure

Explanation: Lexical scope means the scope is determined by the physical placement of code.

Published by Mr. Dubey ⭐ 111.42K Points at 11-Jun-2025 07:19 am in JavaScript

Q. What will be the output of: typeof Promise?

(A) function
(B) object
(C) undefined
(D) promise

💬 Discuss

✅ Correct Answer: (A) function

Explanation: Promise is a constructor function, so typeof Promise returns 'function'.

Published by Mr. Dubey ⭐ 111.42K Points at 11-Jun-2025 07:19 am in JavaScript

Q. What will be the result of await Promise.reject('error') in async function?

(A) Unhandled rejection error
(B) Syntax error
(C) Code continues
(D) undefined

💬 Discuss

✅ Correct Answer: (A) Unhandled rejection error

Explanation: The error must be caught or it results in an unhandled rejection.

Published by Mr. Dubey ⭐ 111.42K Points at 11-Jun-2025 07:19 am in JavaScript

JavaScript MCQs with answers Page - 146

Q. Which method is used to handle errors in Promises?

Q. What is the purpose of async keyword in JavaScript?

Q. What is the purpose of the await keyword?

Q. Which JavaScript feature allows function to access variables from an outer scope?

Q. Which keyword is used to define a class in JavaScript?

Q. How do you create an instance of a class?

Q. Which method is automatically called when a new object is created?

Q. What is lexical scope?

Q. What will be the output of: typeof Promise?

Q. What will be the result of await Promise.reject('error') in async function?

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