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Build your first Express application in minutes. This guide walks you through creating a basic web server with routing, middleware, and static file serving.

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Prerequisites

Before you begin, make sure you have:
  • Node.js 18 or higher installed
  • A text editor or IDE
  • Basic knowledge of JavaScript

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Create Your First Express App

1

Create a project directory

mkdir myapp
cd myapp
2

Initialize your project

npm init -y
3

Install Express

npm install express
4

Create your server file

Create a file named app.js with this code:
app.js
import express from 'express';

const app = express();
const port = 3000;

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

app.listen(port, () => {
  console.log(`Server running at http://localhost:${port}`);
});
If using CommonJS instead of ES modules, use const express = require('express');
5

Update package.json for ES modules

Add "type": "module" to your package.json:
package.json
{
  "name": "myapp",
  "version": "1.0.0",
  "type": "module",
  "main": "app.js"
}
6

Start your server

node app.js
Visit http://localhost:3000 in your browser to see “Hello World!”

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Add More Routes

Expand your application with additional routes: 
app.get('/', (req, res) => {
  res.send('Hello World!');
});

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

app.get('/users/:id', (req, res) => {
  res.send(`User ID: ${req.params.id}`);
});

app.post('/api/data', (req, res) => {
  res.json({ message: 'Data received' });
});

​
Add Middleware

Parse JSON request bodies and log requests: 
import express from 'express';

const app = express();

// Built-in middleware
app.use(express.json());
app.use(express.urlencoded({ extended: true }));

// Custom middleware
app.use((req, res, next) => {
  console.log(`${req.method} ${req.url}`);
  next();
});

app.post('/api/users', (req, res) => {
  console.log(req.body); // Access parsed JSON body
  res.json({ success: true, data: req.body });
});

​
Serve Static Files

Serve static files like HTML, CSS, and images: 
import express from 'express';
import path from 'path';
import { fileURLToPath } from 'url';

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

const app = express();

// Serve static files from 'public' directory
app.use(express.static(path.join(__dirname, 'public')));

app.listen(3000);
Create a public directory and add an index.html file:
public/index.html
<!DOCTYPE html>
<html>
<head>
  <title>My Express App</title>
</head>
<body>
  <h1>Welcome to Express!</h1>
</body>
</html>

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Error Handling

Add basic error handling to your application: 
// 404 handler
app.use((req, res, next) => {
  res.status(404).send('Page not found');
});

// Error handler
app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).send('Something went wrong!');
});

​
Using Environment Variables

Create a .env file for configuration:
.env
PORT=3000
NODE_ENV=development
Install and use the dotenv package: 
npm install dotenv

import 'dotenv/config';
import express from 'express';

const app = express();
const port = process.env.PORT || 3000;

app.listen(port, () => {
  console.log(`Server running on port ${port}`);
});

​
Complete Working Example

Here’s a complete example combining everything:
app.js
import 'dotenv/config';
import express from 'express';
import path from 'path';
import { fileURLToPath } from 'url';

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

const app = express();
const port = process.env.PORT || 3000;

// Middleware
app.use(express.json());
app.use(express.urlencoded({ extended: true }));
app.use(express.static(path.join(__dirname, 'public')));

// Logging middleware
app.use((req, res, next) => {
  console.log(`${new Date().toISOString()} - ${req.method} ${req.url}`);
  next();
});

// Routes
app.get('/', (req, res) => {
  res.send('Hello World!');
});

app.get('/api/status', (req, res) => {
  res.json({ status: 'ok', timestamp: Date.now() });
});

app.get('/users/:id', (req, res) => {
  res.json({ userId: req.params.id, name: 'Sample User' });
});

app.post('/api/users', (req, res) => {
  res.status(201).json({ success: true, data: req.body });
});

// 404 handler
app.use((req, res) => {
  res.status(404).json({ error: 'Not found' });
});

// Error handler
app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).json({ error: 'Internal server error' });
});

app.listen(port, () => {
  console.log(`Server running at http://localhost:${port}`);
});
Use nodemon for automatic server restarts during development:
npm install -D nodemon
npx nodemon app.js

​
Testing Your API

Test your endpoints using curl: 
# GET request
curl http://localhost:3000/api/status

# POST request with JSON
curl -X POST http://localhost:3000/api/users \
  -H "Content-Type: application/json" \
  -d '{"name":"John","email":"[email protected]"}'

# Route with parameters
curl http://localhost:3000/users/123

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Next Steps

Now that you have a working Express application:

Core Concepts

Learn about routing, middleware, and request/response handling

Template Engines

Add dynamic views with EJS, Pug, or Handlebars

Database Integration

Connect to MongoDB, PostgreSQL, or MySQL

API Reference

Explore the complete Express API documentation

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