Getting Started with Express

Why Express?

Express is the most popular Node framework — the E in MERN. (A framework is a ready-made set of tools and shortcuts that does the repetitive plumbing for you, so you write far less code.) It handles routing, requests and responses with clean, simple code instead of the raw http boilerplate you saw earlier. (Boilerplate means the same dull setup code you would otherwise have to type by hand every time.) Since it is a package, you install it with npm first:

npm init -y
npm install express

Now the whole server in a handful of lines:

// server.js
const express = require("express");
const app = express();

app.get("/", (req, res) => {
  res.send("<h1>Hello from Express!</h1>");
});

app.listen(3000, () => console.log("Running on http://localhost:3000"));

Line by line: require("express") loads the framework, and express() creates your app (commonly named app). app.get("/", ...) says "when a browser asks for the home page /, run this function" — and res.send(...) sends a reply back. app.listen(3000, ...) starts the server on port 3000. Compare this to the raw http version: no writeHead, no manual headers — Express handles those for you.

node server.js
# Visit http://localhost:3000  →  Hello from Express!