What you need to know
fetch rejects for certain network failures but normally resolves for HTTP statuses such as 404 or 500. Treating every resolved response as success can make an error page appear as valid data.
How to apply it
Check response.ok before parsing success data, handle expected status codes, and catch network or parsing errors. Keep user-facing messages clear while sending diagnostic details to safe developer logs.
Common mistake to avoid
Do not show raw server responses or stack traces to users. Also avoid retrying every error indefinitely; use limited retries only for operations where they make sense.