What is the correct order for error middleware in Express?

What is the correct order for error middleware in Express?

In Express, error-handling middleware should be defined after all other middleware and routes. It typically looks like this:

app.use('/api', apiRoutes);
app.use(errorHandler);

Can you explain why it needs to be after the routes?

Sure! Error middleware needs to be placed after your routes so that it can catch any errors that occur during the processing of those routes. If it's placed before, it won't have access to the errors thrown by the routes.

What happens if I place it before the routes?

If you place the error middleware before the routes, it won't be able to catch errors from those routes because they haven't been defined yet. This can lead to unhandled errors and unexpected behavior.

Are there any best practices for writing error middleware?

Yes! Some best practices include:

1. Always include four parameters: err, req, res, and next.
2. Log the error for debugging purposes.
3. Send a user-friendly response without exposing sensitive information.