Reliability

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1. 01 Explain `try/catch/finally` semantics, including what happens if `finally` contains a `return`. Medium
2. 02 How do you create and throw custom Error subclasses with additional metadata? Easy
3. 03 Explain the difference between operational errors (expected, e.g., network failure) and programmer errors (bugs). Medium
4. 04 How would you implement a global error boundary for uncaught exceptions and unhandled promise rejections in a web app? Hard
5. 05 Explain the `Error.cause` property and how it helps with error chaining/wrapping. Medium
6. 06 Implement a `safeJsonParse` utility that never throws and returns a Result-like object instead. Easy
7. 07 Given a snippet with a closure-in-loop bug, identify the root cause and propose two different fixes. Medium
8. 08 Given a memory-leak-prone component (uncleared interval on unmount), find and fix the leak. Hard
9. 09 Given code with an off-by-one error in a pagination loop, trace and fix it. Easy
10. 10 A `fetch` call fires twice due to React StrictMode / re-render; diagnose and fix the race condition. Hard
11. 11 Given a deeply nested `this` bug inside a class method passed as a callback, diagnose and fix it. Medium
12. 12 Explain how you'd use `debugger`, breakpoints, watch expressions, and conditional breakpoints in Chrome DevTools to isolate a bug. Medium
13. 13 Given an app freezing on large datasets, use the Performance tab to identify whether it's a JS bottleneck or layout thrashing. Hard
14. 14 Diagnose a bug where an array `sort()` unexpectedly mutates a shared reference used elsewhere. Medium
15. 15 A Promise chain silently swallows an error — identify why and where a `.catch()` is missing. Medium
16. 16 Given intermittent test failures tied to `Date.now()` or timezones, diagnose flaky-test root causes. Hard