Routing and HTTP Methods · Node.js & Express Foundations

Objectives

By the end of this lesson, you should be able to:

Define routes for GET, POST, PUT, and DELETE requests
Explain how Express matches an incoming request to a route
Understand what happens when no route matches

💡 Why this matters: REST APIs (covered fully in Module 9) are built entirely on matching an HTTP method and a URL path to a specific action, create, read, update, delete. Express’s routing is the mechanism that makes each of those a one-line registration instead of a manual check.

⚠️ A note on verification: every snippet and every response shown below was actually run and tested with real HTTP requests.

Routes for Different HTTP Methods

javascript

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

app.get('/', (req, res) => {
  res.send('Homepage');
});

app.get('/about', (req, res) => {
  res.send('About page');
});

app.post('/contact', (req, res) => {
  res.send('Contact form received');
});

app.put('/items/1', (req, res) => {
  res.send('Item 1 updated');
});

app.delete('/items/1', (req, res) => {
  res.send('Item 1 deleted');
});

app.listen(4002);

Testing each route with the matching method:

bash

curl -X GET http://localhost:4002/
curl -X GET http://localhost:4002/about
curl -X POST http://localhost:4002/contact
curl -X PUT http://localhost:4002/items/1
curl -X DELETE http://localhost:4002/items/1

text

Homepage
About page
Contact form received
Item 1 updated
Item 1 deleted

app.get, app.post, app.put, and app.delete each register a handler for that specific HTTP method. A route only matches when both the path and the method match, GET /items/1 and PUT /items/1 are entirely separate routes, even though the path is identical.

What Happens With No Matching Route

bash

curl -i -X POST http://localhost:4002/

text

HTTP/1.1 404 Not Found
Content-Type: text/html; charset=utf-8

<!DOCTYPE html>
<html lang="en">
<head><meta charset="utf-8"><title>Error</title></head>
<body><pre>Cannot POST /</pre></body>
</html>

Express automatically returns a 404 response when no registered route matches a request’s path and method, no code required for this default behavior. Module 8 (Error Handling) covers replacing this default page with a custom one.

Route Matching Order

Express checks routes in the order they’re registered, and uses the first one that matches. This matters once routes could overlap, a specific route like /users/me should typically be registered before a more general pattern like /users/:id (Lesson 4), otherwise the general pattern matches first and the specific route never gets reached.

Try It

Create routes for GET /products, POST /products, and DELETE /products, each responding with distinct plain text.
Test all three with curl, using the correct method for each.
Send a request to a method/path combination you didn’t register, and confirm Express’s default 404 response appears.
Explain, in your own words, why route registration order matters when two routes could both match the same path.

Recap

app.get/post/put/delete register a handler for a specific HTTP method and path, both must match.
Express returns a default 404 response automatically when nothing matches.
Routes are checked in registration order, the first match wins.

Next lesson: the request and response objects every route handler receives.