Node Essentials

An HTTP server

Lesson 5 of 5

What you'll learn

Create an HTTP server with http.createServer
Route by method and path to the right handler
Return JSON with the correct status and headers

An HTTP server is, conceptually, a single function: a request comes in, you produce a response. Node's http module hands you that request/response pair on every connection.

import { createServer } from "node:http";

const server = createServer((req, res) => {
  res.writeHead(200, { "Content-Type": "application/json" });
  res.end(JSON.stringify({ hello: "world" }));
});

server.listen(3000, () => console.log("listening on :3000"));

Routing is a lookup

Real apps serve many endpoints, so you route: combine the method and path into a key, look up a handler, and run it. A missing key is a 404.

const routes = {
  "GET /users": (req) => ({ status: 200, body: { users: [] } }),
  "POST /users": (req) => ({ status: 201, body: { created: true } }),
};

function handle(method, path) {
  const handler = routes[method + " " + path];
  if (!handler) return { status: 404, body: { error: "Not Found" } };
  return handler();
}

Always set the status and type

Forgetting Content-Type: application/json makes clients guess at your payload, and a silent default 200 hides real failures. Set both explicitly on every response.

The challenge builds that router as a pure function — method plus path in, a response object out, with a 404 fallback.

A request router

Run it. The router maps method+path to a handler and returns a response object, falling back to 404 for unknown routes.

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That is the core of every Node backend: route a request to a handler, return a response.

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