JavaScript MCQ Questions with answers and solutions Page 157

Q. Which statement is true for arrow functions?

(A) They bind their own 'this'
(B) They use lexical 'this'
(C) They are block-scoped
(D) They must use function keyword

✅ Correct Answer: (B) They use lexical 'this'

Explanation: Arrow functions do not bind their own this; they inherit from parent.

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

Q. What will be logged?

Code:

let arr = [1, 2, 3];
arr.length = 1;
console.log(arr);

(A) [1]
(B) [1, 2, 3]
(C) []
(D) [1, 2]

💬 Discuss

✅ Correct Answer: (A) [1]

Explanation: Setting length to 1 truncates the array to one element.

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

Q. What is the result of the following?

Code:

console.log(typeof NaN);

(A) NaN
(B) number
(C) undefined
(D) object

💬 Discuss

✅ Correct Answer: (B) number

Explanation: NaN stands for Not-a-Number but its type is 'number'.

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

Q. What will this expression return?

Code:

Boolean([]);

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

💬 Discuss

✅ Correct Answer: (A) true

Explanation: An empty array is a truthy value in JavaScript.

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

Q. Which is not a valid JavaScript data type?

(A) Undefined
(B) Boolean
(C) Float
(D) Symbol

💬 Discuss

✅ Correct Answer: (C) Float

Explanation: JavaScript has no distinct 'float' type, only 'number'.

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

Q. What is the output?

Code:

console.log('2' + 2 - 2);

(A) 22
(B) 2
(C) NaN
(D) 0

💬 Discuss

✅ Correct Answer: (B) 2

Explanation: '2' + 2 = '22'; '22' - 2 = 20.

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

Q. What does the following return?

Code:

[] == ![];

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

💬 Discuss

✅ Correct Answer: (A) true

Explanation: [] is truthy, ![] is false. [] == false is true due to coercion.

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

Q. Which method is used to convert an object to JSON string?

(A) JSON.parse()
(B) JSON.stringify()
(C) toString()
(D) parseJSON()

💬 Discuss

✅ Correct Answer: (B) JSON.stringify()

Explanation: JSON.stringify() converts an object into a JSON string.

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

Q. Which array method returns a new array with only truthy values?

(A) filter()
(B) map()
(C) reduce()
(D) forEach()

💬 Discuss

✅ Correct Answer: (A) filter()

Explanation: filter() creates a new array with elements that pass a test.

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

Q. Which of these is a valid JavaScript variable name?

(A) 1value
(B) $value
(C) var
(D) -value

💬 Discuss

✅ Correct Answer: (B) $value

Explanation: Variable names can begin with $ or _ but not numbers or reserved keywords.

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

JavaScript MCQs with answers Page - 157

Q. Which statement is true for arrow functions?

Q. What will be logged?

Q. What is the result of the following?

Q. What will this expression return?

Q. Which is not a valid JavaScript data type?

Q. What is the output?

Q. What does the following return?

Q. Which method is used to convert an object to JSON string?

Q. Which array method returns a new array with only truthy values?

Q. Which of these is a valid JavaScript variable name?

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