Node.js & Libuv•Part 4: Express, Fastify, APIs & Middleware (36 - 50)
Centralized Global Error Handler in Express.
In Simple Words:
Must accept exactly 4 parameters (err, req, res, next) so Express's reflection inspects fn.length === 4 to recognize it as an error-handling middleware:
javascript
app.use((err, req, res, next) => {
console.error('Global Error Handler:', err.stack);
res.status(err.statusCode || 500).json({
error: { message: err.message, status: err.statusCode || 500 }
});
});