JavaScript Error Handling - Practice Questions 2026
Course Description
Master the art of identifying, isolating, and fixing bugs with the most comprehensive JavaScript Error Handling & Debugging Practice Exams on Udemy. Whether you are preparing for a technical interview or looking to strengthen your production-level coding skills, these practice tests provide the rigorous training necessary to handle complex runtime issues and logic flaws.
Why Serious Learners Choose These Practice Exams
Serious developers understand that writing code is only half the battle; the ability to debug effectively is what separates juniors from seniors. This course is designed for those who want to move beyond basic console.log statements and truly understand the JavaScript engine's error-reporting mechanisms. Our questions are curated to mimic real-world development hurdles, ensuring you gain the confidence to maintain clean, resilient codebases.
Course Structure
The exams are organized into six distinct levels to ensure a logical progression of difficulty:
Basics / Foundations: Focuses on the fundamental types of errors in JavaScript, such as SyntaxErrors and ReferenceErrors. You will learn to identify common mistakes before the code even executes.
Core Concepts: Covers the mechanics of the try...catch...finally block. This section tests your ability to manage synchronous error flows and the scope of variables within catch blocks.
Intermediate Concepts: Dives into the Error object and its properties. You will practice creating custom error classes and throwing meaningful exceptions that help in logging and monitoring.
Advanced Concepts: Tackles the complexities of asynchronous debugging. This includes handling rejected promises, async/await error catching, and global unhandled rejection event listeners.
Real-world Scenarios: Puts you in the shoes of a lead developer fixing bugs in API integrations, DOM manipulations, and state management logic.
Mixed Revision / Final Test: A comprehensive examination featuring a randomized mix of all the above topics to simulate a high-pressure technical assessment or certification environment.
Sample Practice Questions
Question 1
What will be the output of the following code snippet?
JavaScript
try {
throw new Error("Initial Error");
} catch (e) {
throw new Error("Caught Error");
} finally {
console.log("Cleanup Complete");
}
Option 1: Cleanup Complete followed by an Uncaught Error: Initial Error
Option 2: Cleanup Complete followed by an Uncaught Error: Caught Error
Option 3: Caught Error followed by Cleanup Complete
Option 4: Initial Error followed by Cleanup Complete
Option 5: Only Cleanup Complete
Correct Answer: Option 2
Correct Answer Explanation: In JavaScript, the finally block always executes regardless of whether an error was thrown or caught. However, if an error is thrown inside the catch block, it becomes the "pending" exception. The finally block runs first, logging "Cleanup Complete," and then the pending "Caught Error" is thrown to the global scope since there is no outer catch block to handle it.
Wrong Answers Explanation:
Option 1: Incorrect because the error thrown in the catch block overwrites the original "Initial Error."
Option 3: Incorrect because the console.log in the finally block executes before the script terminates due to the uncaught error.
Option 4: Incorrect because the original error was successfully caught and a new one was dispatched.
Option 5: Incorrect because while the log executes, the script still results in an unhandled exception.
Question 2
How does JavaScript handle an error that occurs inside a setTimeout callback function?
Option 1: It can be caught by a try...catch block wrapping the setTimeout call.
Option 2: It is automatically ignored by the engine.
Option 3: It bubbles up to the nearest parent function.
Option 4: It cannot be caught by a wrapping try...catch; it requires a separate try...catch inside the callback.
Option 5: The setTimeout returns an error object instead of a timer ID.
Correct Answer: Option 4
Correct Answer Explanation: Because setTimeout is asynchronous, the wrapping try...catch block finishes executing before the callback function is even added to the task queue. When the callback finally runs and throws an error, the original execution context (the try block) is already gone. Therefore, you must place a try...catch block inside the callback itself to handle errors.
Wrong Answers Explanation:
Option 1: Incorrect because the stack trace of the callback is separate from the code that initiated the timer.
Option 2: Incorrect because unhandled errors in callbacks will still trigger global error events or crash the process.
Option 3: Incorrect because the "parent" function has already finished execution by the time the timer expires.
Option 5: Incorrect because setTimeout always returns a numeric ID (or an object in Node. js) regardless of what happens inside the callback.
Course Benefits
Welcome to the best practice exams to help you prepare for your JavaScript Error Handling & Debugging.
You can retake the exams as many times as you want .
This is a huge original question bank .
You get support from instructors if you have questions .
Each question has a detailed explanation .
Mobile-compatible with the Udemy app .
30-days money-back guaran6tee if you are not satisfied .
We hope that by now you are convinced! And there are a lot more questions inside the course.
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