JavaScript

Writes, debugs, and reviews JavaScript: async and the event loop, coercion, closures, dates, Unicode, regex, and modern ES2023+ APIs. Use when JS throws TypeError or "undefined is not a function", a promise never settles or a rejection goes unhandled, NaN or [object Object] appears, dates shift by a day, sorting or equality misbehaves, memory grows, a regex hangs, JSON loses precision, a Node process won't exit or ignores signals, or fetch doesn't reject on a 404; also when choosing data structures, handling errors, profiling slow code, or checking whether a feature is safe for a target Node or browser version. Covers Node and browser runtime edges. Not for TypeScript type-system design or framework internals.