·10 min read
One BigInt in your log data deletes every other field
One BigInt makes JSON.stringify throw, so your logger drops every other field too. What I measured, and a safe() helper that keeps Dates and Errors intact.
❯grep -rl "#logging" ./posts
#logging
9 posts
·7 min read
Why your serverless function loses its last logs
Batched logs sit in memory until a timer fires. Serverless freezes your function the moment it responds. Here is what I measured, and the one-line fix.
·9 min read
What really happens when two requests share one console.time() label
Everyone says console.time() breaks under concurrency because the second call overwrites the first. I tested it in Node, Bun and Deno, and that is not what happens. The second timer is thrown away, the fast request reports the slow request's duration, and the slow request reports nothing at all.
·12 min read
How to stop your structured logs from silently drifting out of shape
Structured logging only pays off if the data field has a stable shape you can query on. Nothing enforces that by default. Here's how to catch drift with schema validation that never drops the log line, using the Standard Schema spec so it works with Zod, Valibot, or nothing at all.
·8 min read
My debug log rule did nothing, and the reason was the order of the commas
I set LOG_LEVEL to turn on debug logs for one feature. Nothing appeared. The rules were spelled correctly — they were just in the wrong order. Here is what I measured, and the rule that tells you which order is right.
·11 min read
How to catch every uncaught error in a Next.js app, including the ones window.onerror silently misses
window.onerror is the answer everyone gives. It never fires for a broken image, and the next library that loads can delete yours. Here is what to use instead, on the client and on the server, tested in a real browser.
·9 min read
How to turn minified chunk paths in your error logs back into real filenames
A crash at chunks/page.js:1:518 tells you nothing. Source maps turn it back into checkout.ts:3:49. Here's how the lookup works, and the one case where it hands you a real-looking line number that is completely wrong.
·10 min read
Why JSON.stringify(error) prints {} in your logs, and how to actually log an Error properly
Error objects have non-enumerable fields, so a logger that just JSON.stringify's them prints an empty object. Here's why, and a serializer that captures message, stack, cause chains, and AggregateErrors properly.
·8 min read
How to log from the browser straight into your terminal in Next.js (without opening a public endpoint)
The problem with console.log in the browser, why a naive 'POST logs to the server' endpoint is a security hole, and how @developerehsan/nextjs-logger solves both with one import.