Question

How can I create a custom error handler for Express.js?

I'm looking to create a custom error handler in my Express.js application to manage and format error responses consistently across the API. I’d like to understand the setup process, including how to catch different types of errors, send custom error messages, and handle unexpected issues gracefully. What’s the best way to implement a custom error handler in Express.js?

Answer 1

Step 1: Create the Error Handler Middleware

// errorHandler.js

const errorHandler = (err, req, res, next) => {
  const statusCode = err.statusCode || 500;
  const message = err.message || 'Internal Server Error';

  res.status(statusCode).json({
    success: false,
    status: statusCode,
    message: message,
    stack: process.env.NODE_ENV === 'development' ? err.stack : null,
  });
};

module.exports = errorHandler;

Step 2: Use the Error Handler in Your App

// app.js

const express = require('express');
const app = express();
const errorHandler = require('./errorHandler');

// ... your routes and other middleware

// Error handler middleware (must be added last)
app.use(errorHandler);