Troubleshooting
The symptom, the cause, and the fix for the bugs that reliably bite every developer once.
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Why your React effect runs twice in dev
React StrictMode double-invokes effects in development on purpose. Here's why, what it's catching, and how to write effects that survive it — with proper cleanup.
Why your Express async errors slip through
A rejected promise in an async route handler never reaches your Express error middleware. Here's why the default error handler misses it, and three ways to fix it.