How do you handle errors inside a Web Worker? What events are available and what information do they expose?

0-2 years experience

1. 1You need to fetch data in a Web Worker and want to log any errors that occur. How would you set up error handling inside the worker and in the main thread?
2. 2If a worker throws a ReferenceError, what event fires on the main thread and what properties can you inspect to understand the failure?

2-5 years experience

1. 1During a feature rollout, a worker sometimes crashes with an uncaught exception. Walk me through how you'd debug it using the events available.
2. 2You notice that errors from a worker aren't reaching your logging service. What could be going wrong with your error handling setup, and how would you fix it?
3. 3Explain the trade‑offs between handling errors inside the worker with try/catch versus relying on the worker's onerror event.

5-8 years experience

1. 1Design a robust error‑handling layer for a system that spawns many workers to process user uploads. How would you capture, aggregate, and react to errors across workers without leaking resources?
2. 2When a worker encounters an error, you need to decide whether to restart it or fallback to a main‑thread implementation. What factors influence that decision, and how would you implement the logic?
3. 3Discuss how you would instrument error events to work with a centralized monitoring system while preserving performance.

8+ years experience

1. 1Our platform plans to migrate several CPU‑intensive services to Web Workers across multiple teams. How would you define a cross‑team strategy for error handling, reporting, and versioning of worker scripts?
2. 2Consider a legacy codebase where workers were created without any error handling. Propose a phased approach to retrofit error handling and ensure backward compatibility.
3. 3What architectural patterns could you use to isolate worker failures so they don't cascade into the main application, especially under high load?