Add Centralized Error Handling Middleware in Express

Use this AI prompt to create a global error-handling middleware for Express that formats error responses, logs issues, and prevents crashes in production.

🧠 What This Prompt Does

This AI prompt helps you implement a centralized error-handling middleware for Express.
It provides uniform error responses, logs issues for debugging, and prevents unhandled rejections from crashing your app.

💬 The Prompt

You are a backend engineer.
Generate a centralized error-handling middleware for Express.

Requirements:

- Catch all thrown or forwarded errors
- Log error message and stack trace
- Send structured JSON response
- Hide internal details in production
- Include example usage

🚀 Example Output (AI Generated)

// middleware/errorHandler.js
export const errorHandler = (err, req, res, next) => {
  console.error('Error:', err.message);

  const status = err.statusCode || 500;
  const message =
    process.env.NODE_ENV === 'production'
      ? 'Internal Server Error'
      : err.message;

  res.status(status).json({
    success: false,
    message,
    ...(process.env.NODE_ENV !== 'production' && { stack: err.stack }),
  });
};

// Example usage:
import express from 'express';
import { errorHandler } from './middleware/errorHandler.js';
const app = express();

app.use('/api', routes);
app.use(errorHandler);

📘 When to Use This Prompt

• For consistent error responses in all APIs.
• When logging or debugging issues in production.
• To simplify try-catch logic across your app.

💡 Best Practices

• Always next(err) in async routes to forward errors.
• Avoid leaking sensitive data in error messages.
• Combine this with Winston or Pino for structured logging.
• Define custom error classes for known issues.

🏁 Summary

This prompt helps you build a robust error-handling system in Express — providing consistent responses and stable, maintainable backend behavior.