Error Handling Best Practices in Node.js: A Comprehensive Guide

Error handling is a crucial aspect of building robust Node.js applications. When done right, it can mean the difference between a gracefully degrading application and one that crashes unexpectedly. Let’s explore the best practices that can help you manage errors effectively in your Node.js projects.

Understanding Error Types in Node.js

Before diving into best practices, it’s essential to understand the different types of errors you might encounter:

• Operational Errors: Expected errors that occur during normal operation (file not found, network timeout)
• Programming Errors: Bugs in the code (trying to read undefined, type errors)
• System Errors: Issues with system resources (out of memory, too many files open)

Best Practices for Error Handling

1. Use Async/Await with Try-Catch

async function getUserData(userId) {
    try {
        const user = await database.findUser(userId);
        return user;
    } catch (error) {
        logger.error('Failed to fetch user:', error);
        throw new CustomError('UserFetchError', 'Unable to retrieve user data');
    }
}

2. Create Custom Error Classes

class CustomError extends Error {
    constructor(name, message, statusCode = 500) {
        super(message);
        this.name = name;
        this.statusCode = statusCode;
    }
}

3. Implement Global Error Handling

process.on('uncaughtException', (error) => {
    logger.error('Uncaught Exception:', error);
    // Perform cleanup operations
    process.exit(1);
});

process.on('unhandledRejection', (reason, promise) => {
    logger.error('Unhandled Rejection at:', promise, 'reason:', reason);
    // Handle the error appropriately
});

4. Use Error Middleware in Express

app.use((error, req, res, next) => {
    logger.error(error.stack);
    res.status(error.statusCode || 500).json({
        status: 'error',
        message: error.message || 'Internal server error'
    });
});

5. Proper Error Logging

• Log errors with different severity levels
• Include relevant context and stack traces
• Use structured logging formats
• Implement log rotation and management

6. Error Recovery Strategies

• Implement retry mechanisms for transient failures
• Use circuit breakers for external service calls
• Provide fallback behaviors when possible
• Plan for graceful degradation

Best Practices for Production

1. Never send stack traces to clients
2. Use appropriate HTTP status codes
3. Implement rate limiting for error-prone endpoints
4. Monitor and alert on error patterns
5. Document error responses in API documentation

Remember, good error handling is not just about catching errors – it’s about providing meaningful feedback, maintaining system stability, and ensuring a great user experience even when things go wrong.