Stack Trace Explainer — illustrative example

INPUT
TypeError occurs when code reads user.name and user is undefined.

RESULT
Check where user should be assigned and why it is absent; choose appropriate missing-user handling rather than hiding every error.

REVIEW
A stack trace shows the path to a failure, not necessarily its original cause. Find the relevant application frame and inspect the data reaching it.

This is a teaching example, not a live execution record.