framework
Express Errors
Express errors: 'Cannot set headers after they are sent', 'TypeError: req.body is undefined', 'PayloadTooLargeError', middleware error not caught, missing next() call, async error not propagated.
Express's biggest gotcha: async errors aren't caught by the default error middleware. Use express-async-errors or wrap handlers in try/catch with next(err). 'Cannot set headers after they are sent' = double res.send/res.json call, often from missing return after a response. body-parser errors (PayloadTooLargeError) need explicit limits.
Official docs
https://expressjs.com/en/guide/error-handling.html
Support
https://expressjs.com/en/resources/community.html