Node.js Error Handling

Node.js Error Handling

Error handling in Node.js is the process of catching and managing problems that occur during code execution.
Since Node.js uses asynchronous operations, proper error handling is extremely important to avoid crashes and improve stability.

✅ Types of Errors in Node.js

1️⃣ Synchronous Errors

Errors that happen immediately during code execution.

2️⃣ Asynchronous Errors

Errors from asynchronous operations (file reading, API calls, DB queries).

⭐ Error Handling Techniques in Node.js

1️⃣ Handling Synchronous Errors (try…catch)

2️⃣ Handling Errors in Callbacks

Node.js uses a standard pattern for callbacks:

Example:

✔ First parameter is always error
✔ You must check err before using data

3️⃣ Handling Errors in Promises

Using .catch():

Using .then() and .catch():

4️⃣ Handling Errors with async/await

Use try...catch inside async functions:

5️⃣ Global Error Handling

Node.js provides global handlers to catch unexpected crashes.

A. Uncaught Exception (Synchronous Errors)

⚠ Should be used only for logging → not to continue the app.

B. Unhandled Promise Rejection

Useful for tracking missing .catch().

⚠ Why Proper Error Handling Is Important

✔ Prevents application crashes
✔ Helps debugging
✔ Improves user experience
✔ Ensures stability in production
✔ Avoids server downtime

Common Error Handling Patterns in Node.js

⭐ 1. Throwing Custom Errors

⭐ 2. Returning Errors Gracefully

⭐ 3. Using Express Error Middleware (in Web Apps)

Best Practices for Error Handling in Node.js

✔ Always return errors in async callbacks
✔ Use try...catch with async/await
✔ Log errors properly
✔ Use centralized error handlers
✔ Never ignore promise rejections
✔ Don’t expose internal error messages to users
✔ Avoid using throw inside asynchronous callbacks (use reject instead)

Summary Table