Error Handling Project — Complete Error System

In this tutorial, you will learn about Error Handling Project. We cover key concepts, practical examples, and best practices to help you master this topic.

This capstone project combines all previous lessons to build a complete error handling system for a REST API with custom error classes, global middleware, validation, logging, and monitoring.

Project Overview

Build an error handling system with:

• Custom error class hierarchy
• Error Factory functions for all common status codes
• Global error handler middleware
• Field-level validation error reporting
• Structured error logging
• Sentry integration for monitoring
• OpenAPI documentation for all error responses

Implementation

class ApiError extends Error { }
class NotFoundError extends ApiError { }
class ValidationError extends ApiError { }
class AuthError extends ApiError { }
class ConflictError extends ApiError { }
class RateLimitError extends ApiError { }

// Error factories
const Errors = { notFound, validation, unauthorized, forbidden, conflict, rateLimited, internal };

// Global handler
app.use(errorHandler);

// Validation middleware
function validate(schema) {
  return (req, res, next) => {
    const errors = validateSchema(schema, req.body);
    if (errors) throw Errors.validation(errors);
    next();
  };
}

// Structured logging
const logger = createStructuredLogger();

// Monitoring
Sentry.init({ ... });

Checklist

• Custom error class hierarchy
• Error factory functions
• Global error handler middleware
• Field-level validation errors
• Consistent error response format
• Request ID on all errors
• Structured error logging
• Error monitoring integration
• All error responses documented in OpenAPI
• 5xx errors trigger alerts

Challenge

Implement the complete system and verify that every endpoint returns consistent error responses for all error scenarios.