Error Handling in Routes

In Express applications, errors can arise from various sources, including invalid client requests, missing parameters, and server failures. Properly handling these errors ensures that users receive meaningful feedback while preventing crashes or security vulnerabilities.

Errors generally fall into two categories:

• Client errors (4xx) occur when users send invalid requests, such as missing required parameters or unauthorized access attempts.

• Server errors (5xx) result from internal failures, such as database issues or unhandled exceptions.

Let’s explore different techniques to handle errors efficiently in Express routes.

What happens when an error occurs in Express?

When an error is thrown in a route and not handled, Express catches it and returns a generic “500 Internal Server Error” response. This is part of Express’s built-in error handling.

However, this default behavior is limited. It works only for synchronous errors, doesn’t support custom error messages or JSON responses, and may expose internal stack traces in development.

We need more control over how errors are handled and reported to build reliable APIs and user-facing applications. That’s where custom error handling logic and middleware come in.

Handling errors in synchronous routes

Error handling is straightforward in synchronous code. We can use a try-catch block to catch errors and pass them to Express’s error-handling middleware using the next() function.