Module Overview

What You’ll Learn

• Handle errors correctly in both synchronous and asynchronous Express code
• Pass errors to Express with next()
• Build custom error classes and a single global error handler

💡 Why this module matters: An Express app that doesn’t handle errors correctly either crashes entirely or silently returns the wrong response, neither of which is acceptable in a real application. This module covers the actual, correct pattern for every kind of error Express code runs into.

What’s Covered

• try/catch, catching errors in synchronous code.
• Async error handling, why a rejected promise inside a route needs special care in Express.
• next(), how Express expects an error to be reported from inside middleware or a route.
• Custom error classes, representing different kinds of failure with real, meaningful types.
• A global error handler, one place where every error in the app ends up.

Hands-On

By the end of this module, you’ll have a complete, working error-handling setup: custom error classes, correct async error handling, and a single global error handler catching everything consistently.

Next module: REST API design, the conventions that make an API predictable to use.