JavaScript MCQ Questions with answers and solutions Page 156

Q. Which value is returned when a function doesn't explicitly return anything?

(A) null
(B) undefined
(C) false
(D) 0

💬 Discuss

✅ Correct Answer: (B) undefined

Explanation: A function with no return returns undefined.

Published by Chandani ⭐ 10.97K Points at 14-Jun-2025 07:40 am in JavaScript

Q. How can you clone an object in JavaScript?

(A) Object.clone(obj)
(B) obj.copy()
(C) Object.assign({}, obj)
(D) clone(obj)

💬 Discuss

✅ Correct Answer: (C) Object.assign({}, obj)

Explanation: Object.assign({}, obj) creates a shallow copy of obj.

Published by Chandani ⭐ 10.97K Points at 14-Jun-2025 07:40 am in JavaScript

Q. What does the 'await' keyword do?

(A) Pauses the function until a promise settles
(B) Pauses script execution globally
(C) Rejects promises
(D) Creates a new thread

💬 Discuss

✅ Correct Answer: (A) Pauses the function until a promise settles

Explanation: await pauses an async function until the promise settles.

Published by Chandani ⭐ 10.97K Points at 14-Jun-2025 07:40 am in JavaScript

Q. What is the output?

Code:

console.log(3 > 2 > 1);

(A) true
(B) false
(C) undefined
(D) NaN

💬 Discuss

✅ Correct Answer: (B) false

Explanation: 3 > 2 is true (1), then 1 > 1 is false.

Published by Chandani ⭐ 10.97K Points at 14-Jun-2025 07:40 am in JavaScript

Q. What type is returned by Array.isArray([])?

(A) boolean
(B) string
(C) object
(D) undefined

💬 Discuss

✅ Correct Answer: (A) boolean

Explanation: Array.isArray returns a boolean indicating if input is an array.

Published by Chandani ⭐ 10.97K Points at 14-Jun-2025 07:40 am in JavaScript

Q. Which method returns the first index of an element?

(A) search()
(B) findIndex()
(C) indexOf()
(D) find()

💬 Discuss

✅ Correct Answer: (C) indexOf()

Explanation: indexOf() returns the first index of a matching element.

Published by Chandani ⭐ 10.97K Points at 14-Jun-2025 07:40 am in JavaScript

Q. Which of the following is true about 'const'?

(A) Cannot be reassigned
(B) Cannot be mutated
(C) Not block-scoped
(D) Hoisted to top with undefined

💬 Discuss

✅ Correct Answer: (A) Cannot be reassigned

Explanation: const variables cannot be reassigned but can be mutated (for objects).

Published by Chandani ⭐ 10.97K Points at 14-Jun-2025 07:40 am in JavaScript

Q. What will this return?

Code:

console.log('10' - '4' - '3' - 2 + '5');

(A) 15
(B) 1
(C) 15
(D) 15undefined

💬 Discuss

✅ Correct Answer: (C) 15

Explanation: '10' - '4' - '3' - 2 = 1, then 1 + '5' = '15'.

Published by Chandani ⭐ 10.97K Points at 14-Jun-2025 07:40 am in JavaScript

Q. Which statement is true about let, var, and const?

(A) var is block scoped
(B) let is function scoped
(C) const must be initialized
(D) const can be reassigned

💬 Discuss

✅ Correct Answer: (C) const must be initialized

Explanation: const must be initialized when declared.

Published by Chandani ⭐ 10.97K Points at 14-Jun-2025 07:40 am in JavaScript

Q. How to convert a string to an integer in JavaScript?

(A) parseInt(str)
(B) Number(str)
(C) +str
(D) All of the above

💬 Discuss

✅ Correct Answer: (D) All of the above

Explanation: All mentioned methods can convert string to number.

Published by Chandani ⭐ 10.97K Points at 14-Jun-2025 07:40 am in JavaScript

JavaScript MCQs with answers Page - 156

Q. Which value is returned when a function doesn't explicitly return anything?

Q. How can you clone an object in JavaScript?

Q. What does the 'await' keyword do?

Q. What is the output?

Q. What type is returned by Array.isArray([])?

Q. Which method returns the first index of an element?

Q. Which of the following is true about 'const'?

Q. What will this return?

Q. Which statement is true about let, var, and const?

Q. How to convert a string to an integer in JavaScript?

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