Node.js Error Handling

Why Is Error Handling Important?

• Prevents unexpected crashes
• Improves debugging and user experience
• Enables graceful recovery from failures
• Ensures application resilience and security

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Types of Errors in Node.js

1. Synchronous Errors

These occur during code execution and are handled using try...catch:

2. Asynchronous Errors (Callback-based)

In callback-based APIs, errors are usually the first argument:

3. Promise-based Errors

Handled with .catch() or try...catch inside async functions:

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Centralized Error Handling (Express.js Example)

Helps manage errors from all routes in one place.

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Handling Uncaught Exceptions

Used as a last resort to catch uncaught errors:

Note: Crashing the process is safer than running in an unstable state.

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Handling Unhandled Promise Rejections

Avoid silent failures from rejected Promises:

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Throwing Custom Errors

Custom error classes help structure error types:

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Best Practices

• Always handle errors in asynchronous code
• Log errors and respond with meaningful messages
• Avoid throw in async functions unless inside try...catch
• Validate all user input
• Use centralized error handling in larger apps
• Never expose internal errors to users

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Key Takeaways

• Node.js provides multiple ways to handle errors: try/catch, callback, Promises, async/await
• Proper error handling improves stability and maintainability
• Use custom classes and centralized handling for clean error management
• Always catch uncaught exceptions and unhandled rejections
• Prevent errors with defensive programming and input validation