Routing & Middleware
Master Express architecture! Learn how middleware works and how to organize your routes.
Master Express architecture! Learn how middleware works and how to organize your routes. This hands-on tutorial focuses on practical implementation of routing & middleware concepts.
Routing & Middleware
In Express, everything is Middleware. It's the most important concept to understand.
1. What is Middleware? 🧱
Middleware is a function that runs between the request coming in and the response going out. It sits "in the middle".
It has access to:
req(Request)res(Response)next(A function to pass control to the next middleware)
If you forget next(): The request will hang forever! ⏳
2. Built-in Middleware 📦
Express comes with some essential middleware.
express.json(): Parses incoming JSON data (crucial for APIs).express.static(): Serves static files.
3. Organizing Routes (Router) 🚏
Putting all routes in app.js gets messy. Use express.Router to split them into files.
File: routes/users.js
File: app.js
4. Error Handling Middleware 🚨
This is a special middleware with 4 arguments: (err, req, res, next). Express recognizes it by the argument count.
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Quiz
Quiz
Question 1 of 4What is the purpose of the 'next' function?
Key Takeaways
✅ Middleware functions run in a chain.
✅ next() passes the baton.
✅ express.json() is vital for APIs.
✅ express.Router keeps code organized.
✅ Error Handlers catch crashes.
What's Next?
Now that we know how to route, let's build a real API. Next up: Building REST APIs!
Keep coding! 🚀