JavaScript Objective Questions and Answers

This JavaScript quiz contains carefully curated objective questions with correct answers and clear explanations. It is designed for frontend and backend developers, interview preparation, and deep understanding of modern JavaScript concepts including ES6+, asynchronous behavior, scope, closures, and performance pitfalls.

Practice JavaScript MCQs with Detailed Explanations

Answer at least 12 questions to submit.

16

Which queue executes first in the event loop?

High
17

What is the output? Promise.resolve(1) .then(x => x + 1) .then(x => { throw x; }) .catch(err => console.log(err));

High
18

Which statement about prototypes is correct?

Medium
19

What does this keyword refer to inside an arrow function?

Medium
20

What is the output? console.log(typeof (() => {}));

Medium
21

What will be the output order? console.log('A'); setTimeout(() => console.log('B')); Promise.resolve().then(() => console.log('C')); console.log('D');

High
22

What is the output? async function test() { return 5; } console.log(test());

Medium
23

What does await do internally?

High
24

Which causes a memory leak in JavaScript?

High
25

What is the output? let a = { x: 1 }; let b = a; a = null; console.log(b.x);

Medium
26

Which comparison avoids type coercion?

Medium
27

What will be logged? console.log(1 + '2' + 3);

Medium
28

What is the output? console.log(true + false);

Medium
29

Which object is responsible for garbage collection?

High
30

What happens if a Promise is neither resolved nor rejected?

Medium