Node.js Lesson 7: Express.js Basics

Express.js is the most popular Node.js framework. It makes building web servers and APIs much faster and cleaner than the raw http module.

Setup

npm install express

# Install nodemon for auto-restart:
npm install -D nodemon

# Add to package.json scripts:
"dev": "nodemon app.js"

Your First Express App

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

// Parse JSON request bodies
app.use(express.json());

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

app.get("/api/hello", (req, res) => {
  res.json({ message: "Hello!", timestamp: new Date() });
});

app.get("/api/users/:id", (req, res) => {
  const { id } = req.params;
  res.json({ userId: id, name: "User " + id });
});

// Start server
app.listen(3000, () => {
  console.log("Server running on http://localhost:3000");
});

Request Object

app.get("/search", (req, res) => {
  // Query strings: /search?q=node&limit=10
  const { q, limit = 10 } = req.query;
  res.json({ query: q, limit: Number(limit) });
});

app.post("/users", (req, res) => {
  // JSON body from POST request
  const { name, email } = req.body;
  res.status(201).json({ id: Date.now(), name, email });
});