Create a First ExpressJS Application

Express is a popular web framework for Node.js, designed to help you quickly and easily build web applications and APIs. This article will guide you in creating a simple Express application and configuring basic routes.

Prerequisites

Before starting, ensure you have:

Node.js and NPM installed on your machine (if not, refer to the guide linked below).
Basic knowledge of JavaScript and Node.js .
A text editor (e.g., VS Code ).

Step 1: Install Node.js and Express

1. Install Node.js

If you haven’t installed Node.js yet, download and install it from nodejs.org . Verify the installation by running:

node -v
npm -v

If you need help, check this guide: Installing NodeJS and NPM on macOS, Windows, and Linux .

2. Initialize a Node.js Project

Open your terminal and create a new directory for your Express application:

mkdir express-example-app
cd express-example-app

3. Install Express

Install Express in your project. We’ll use express-generator for faster setup:

# Install express-generator globally
npm install -g express-generator@4

# Use express-generator to create a quick setup
npx express-generator --git

4. Install Dependencies

Run the following command to install project dependencies:

npm install

5. Start the Application

After setting up your application, start it with:

npm start

Your application will run on port 3000 (or the port specified in the PORT environment variable). You can access it in your browser at http://localhost:3000 .

ExpressJS Demo

Directory Structure

The default directory structure generated by express-generator version 4 looks like this: ExpressJS Demo

Step 2: Create the Main Application File

Create a new file app.js in your project directory:

touch app.js

Open app.js and configure a basic Express application:

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

// Configure the port for the application
const PORT = process.env.PORT || 3000;

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

// Start the application
app.listen(PORT, () => {
  console.log(`Server is running on http://localhost:${PORT}`);
});

Auto-Reload Configuration

Install nodemon to automatically restart the Node.js server when files change:

npm install nodemon -g

Update the scripts section in package.json:

"scripts": {
  "start": "nodemon ./bin/www",
  "start:watch": "nodemon ./bin/www"
},

Run the application with:

npm run start:watch

Step 3: Create a Simple API

Add a New Route

Create a new file routes/products.js with the following content:

const express = require('express');
const router = express.Router();

/* GET products listing. */
router.get('/', (req, res) => {
  const products = [
    { id: 1, name: 'Laptop', price: 1000 },
    { id: 2, name: 'Mobile', price: 500 },
    { id: 3, name: 'Tablet', price: 300 },
  ];
  res.json(products);
});

module.exports = router;

Register the Route

Open app.js and add the following:

const productsRouter = require('./routes/products');

app.use('/api/products', productsRouter);

Test the API

Visit http://localhost:3000/api/products in your browser or Postman to see the results.

ExpressJS Simple API

Conclusion

Congratulations! You’ve successfully created a simple Express application with basic routes. Express is a powerful and flexible framework that allows you to quickly build web applications and APIs.

Source Code

View the demo source code here: https://github.com/ducxinh/express-example-app

Next Steps

Here are some ways to expand your project:

Routing, Middleware, and Error Handling
Deployment : Deploy the app to a server or cloud platforms like Heroku, AWS, or DigitalOcean.
Database Integration : Connect to databases like MongoDB, MySQL, or PostgreSQL for data storage and retrieval.
Authentication : Secure routes using JWT or OAuth for user authentication.
API Routes : Build RESTful API routes for frontend applications.