Parse query parameters

Before this hits the handler team, make the query parsing easy to audit. Put the important values up front: show raw query string, parsed keys, coercions applied, defaults used, and any validation failures. Flag any unknown parameters and suggest whether they look like a typo of expected keys. Return a clean params object plus a one-line summary for the reviewer.

I invoked a page and the handler threw an error because userId parsed to NaN. The URL came from a marketing email link. I validated my parsing code and it looks straightforward, but I do not know whether the campaign inserted broken links or whether our parser mishandled PLUS signs and encodings. What is the most likely diagnosis and the immediate tests to confirm and fix it?

Over the last quarter I keep patching route handlers for query parsing edge cases: different encoding, missing defaults, and inconsistent validation. Each fix is small but I waste time. Which single change or coding standard should I adopt to stop this recurring churn and make new handlers reliable out of the box?