Eye Training · try / catch / finally

A try only protects what actually fails inside it. Most error-handling bugs are about what slips out.

Part 2 · Surface 11. Bug counts are hidden and some snippets are clean. See Start Here for how to use these drills.

J · The basics

M · Three years in, these should jump out

S · Where seniors stand out

What your eye checks

Whenever you see a try, ask:

1. Is the failure actually inside it? Missing await, a return without await, or a callback that runs later all escape the try.
2. What does the catch do with it? Swallow it, log and carry on, convert it, or rethrow it? Does the caller find out?
3. Can the catch itself throw? A wrong variable name, a property of undefined, or another await in the catch.
4. Which errors does it catch, and what does it turn them into? A catch-all that maps everything to 404, null or "invalid input" hides real outages.
5. Is the original error kept? Throw Error objects, never strings, and wrap with { cause: err }.
6. Is the half-done work undone? A transaction needs a rollback; a multi-step change needs compensation.
7. Is finally only cleaning up? No return or throw in it, and the resource is acquired before the try.
8. Retries: is the error retryable, is the work idempotent, and is there backoff with jitter?

Tells

The visual cue that should make your eye stop:

Go deeper

• Async/Await Traps: return await, missing awaits and unhandled rejections, in depth
• The Node Process Under Failure: uncaught exceptions, unhandled rejections and graceful shutdown
• Next surface: Promises and async/await