Error Handling - Express.js

expressjs-error-middleware.js

const express = require('express');
const app = express();

// Route handler
app.get('/users/:id', (req, res, next) => {
  const userId = req.params.id;

  // Simulating an error when user is not found
  if (!getUserById(userId)) {
    const error = new Error('User not found');
    error.statusCode = 404;
    next(error);
  } else {
    // If user is found, send the user data as response
    const user = getUserById(userId);
    res.json(user);
  }
});

// Error handling middleware
app.use((err, req, res, next) => {
  // Default error status code
  const statusCode = err.statusCode || 500;

  // Default error message
  const message = err.message || 'Internal Server Error';

  // Sending the error response
  res.status(statusCode).json({ error: message });
});

// Starting the server
app.listen(3000, () => {
  console.log('Server is listening on port 3000');
});