How to create your first Express server and handle requests
require express, app.listen, port binding, req object, res object, res.send vs res.json, HTTP methods in Express
Creating an Express Server
Every Express app starts the same way: create the app, define routes, bind to a port. The req and res objects are the core of every request handler.
Minimal working server
const express = require('express');
const app = express();
const PORT = 3000;
app.get('/', (req, res) => {
res.send('Server is running');
});
app.get('/json', (req, res) => {
res.json({ status: 'ok', message: 'Hello from Express' });
});
app.listen(PORT, () => {
console.log(`Server running on http://localhost:${PORT}`);
});Key objects:
req— incoming request (URL, headers, body, params)res— outgoing response (send data back to client)
res.send() sends a string or buffer with Content-Type: text/html. res.json() serializes an object and sets Content-Type: application/json automatically — always use res.json() for API responses.
app.listen() binds the server to a port. The callback fires once the server is ready. Store the port in a variable so you can change it from an environment variable later: const PORT = process.env.PORT || 3000.