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🟨JavaScriptIntermediate

Error Handling: try/catch/finally and throw

📌 Definition:

JavaScript handles runtime errors with try/catch/finally blocks and the throw statement. Proper error handling makes tests and applications fail clearly instead of crashing silently.

📖 Detailed Explanation:

Code that might fail goes in try; if an error is thrown, control jumps to catch(err) with the Error object; finally runs regardless of success or failure (cleanup, closing resources). You throw errors with throw new Error('message') — always throw Error objects (not strings) so you get a stack trace and a consistent .message/.name. For asynchronous code, a rejected promise is caught by .catch() or by try/catch around await. Unhandled rejections and thrown errors bubble up; in Node they can crash the process, so catch at appropriate boundaries. Custom error classes (class ValidationError extends Error) let callers distinguish error types.

🔑 Key Points:
  • try runs risky code; catch handles the thrown Error; finally always runs
  • throw new Error(...) — throw Error objects, not strings
  • await errors are caught with try/catch; promise errors with .catch
  • Custom Error subclasses let you branch on error type
🌍 Real-World Example:

A test teardown uses finally to always close a DB connection or browser context even if an assertion throws mid-test: try { await runSteps(); } catch (e) { logFailure(e); throw e; } finally { await browser.close(); } — guaranteeing cleanup regardless of pass/fail.

🎯 Scenario-Based Interview Question:

Does a return statement inside try skip the finally block? Explain the execution order.

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