JavaScript Asynchronous Programming - Practice Question 2026 - Free Online Course

Master the art of non-blocking code with the most comprehensive JavaScript Asynchronous Programming Practice Exams on Udemy. Whether you are preparing for technical interviews or building complex, high-performance web applications, understanding how JavaScript handles time-consuming operations is non-negotiable.

Welcome to the best practice exams to help you prepare for your JavaScript Asynchronous Programming

Mastering the Event Loop, Promises, and Async/Await is often the biggest hurdle for web developers. This course is designed to bridge the gap between theoretical knowledge and practical mastery through rigorous, high-quality testing.

Retake exams indefinitely: You can retake the exams as many times as you want to ensure total mastery.
Original question bank: This is a huge original question bank curated to reflect modern JavaScript standards (ES6+).
Expert support: You get support from instructors if you have questions regarding any concept.
In-depth learning: Each question has a detailed explanation to ensure you understand the "why" behind the code.
Learn on the go: Mobile-compatible with the Udemy app for practicing anywhere, anytime.
Risk-free enrollment: 30-days money-back guarantee if you are not satisfied with the content.

Why Serious Learners Choose These Practice Exams

In a typical coding environment, a misunderstanding of asynchronous flow leads to race conditions, memory leaks, and "callback hell." Serious learners choose these exams because they do not just test your ability to memorize syntax; they test your ability to predict code execution order and debug complex logic. We focus on the internal mechanics of the JavaScript engine, ensuring you can confidently explain the stack, heap, and queue to any interviewer.

Course Structure

Basics / Foundations: We begin by testing your understanding of synchronous vs. asynchronous execution. This section covers the single-threaded nature of JavaScript and the role of the call stack.
Core Concepts: Dive deep into the original patterns of asynchrony. You will face questions on callbacks, higher-order functions, and the "inversion of control" problem.
Intermediate Concepts: This module focuses heavily on the Promise API. You will be tested on Promise states (Pending, Fulfilled, Rejected), chaining, and basic error handling using .catch().
Advanced Concepts: Tackle the heavy hitters of modern JS. This includes the Event Loop, Microtask Queue vs. Macrotask Queue, and the internal workings of Async/Await.
Real-world Scenarios: Apply your knowledge to practical problems. You will solve questions related to Fetch API calls, debouncing, throttling, and managing multiple concurrent requests.
Mixed Revision / Final Test: A comprehensive final exam that pulls from all previous sections to simulate a high-pressure technical interview environment.

Sample Practice Questions

QUESTION 1

What will be the output of the following code?

JavaScript

console. log('A');

setTimeout(() => console. log('B'), 0);

Promise. resolve(). then(() => console. log('C'));

console. log('D');

OPTION 1: A, B, C, D
OPTION 2: A, D, B, C
OPTION 3: A, D, C, B
OPTION 4: A, C, D, B
OPTION 5: D, A, C, B

CORRECT ANSWER: OPTION 3

CORRECT ANSWER EXPLANATION:

The execution follows the Event Loop order. 1. Synchronous tasks run first (A and D). 2. Microtasks (Promises) run after the current task but before the next Macrotask (C). 3. Macrotasks (setTimeout) run last, even if the delay is 0. Therefore, the order is A, D, C, B.

WRONG ANSWERS EXPLANATION:

OPTION 1: Incorrect because it assumes JavaScript executes code strictly line-by-line without an Event Loop.
OPTION 2: Incorrect because it places the Macrotask (B) before the Microtask (C).
OPTION 4: Incorrect because 'D' is synchronous and must execute before the Promise resolution starts.
OPTION 5: Incorrect because 'A' is the first synchronous call and must appear first.

QUESTION 2

What state is a Promise in after the resolve() function is called but before the .then() callback is executed?

OPTION 1: Pending
OPTION 2: Fulfilled
OPTION 3: Rejected
OPTION 4: Settled
OPTION 5: Both Fulfilled and Settled

CORRECT ANSWER: OPTION 5

CORRECT ANSWER EXPLANATION:

Once resolve() is called, the Promise transitions from 'Pending' to 'Fulfilled'. 'Settled' is a general term used to describe a Promise that is no longer 'Pending' (it is either Fulfilled or Rejected). Therefore, both terms apply accurately.

WRONG ANSWERS EXPLANATION:

OPTION 1: Incorrect because 'Pending' is the initial state before any resolution or rejection occurs.
OPTION 2: This is partially correct but incomplete compared to Option 5.
OPTION 3: Incorrect because resolve() results in fulfillment, not rejection.
OPTION 4: This is partially correct but incomplete as it does not specify the successful nature of the state.

We hope that by now you are convinced! And there are a lot more questions inside the course.