Introduction

Node.js is a powerful runtime for executing JavaScript outside the browser. It allows developers to build scalable, fast, and efficient server-side applications. Express.js, a lightweight and flexible Node.js framework, simplifies the process of building web applications and APIs.

In this guide, we’ll walk you through setting up a basic Node.js application using Express, covering installation, project setup, routing, middleware, and running the server.

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1. Prerequisites

Before we begin, ensure you have the following installed on your system:

• Node.js (Download from nodejs.org)
• npm (Node Package Manager) (Comes with Node.js)
• A text editor (e.g., VS Code)
• A terminal or command prompt

To check if Node.js and npm are installed, run:

node -v  # Check Node.js version
npm -v   # Check npm version

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2. Setting Up a New Node.js Project

Step 1: Create a Project Directory

Navigate to the folder where you want to create your project and run:

mkdir my-express-app
cd my-express-app

Step 2: Initialize a Node.js Project

Run the following command to initialize a new Node.js project:

npm init -y

This will create a package.json file with default settings.

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3. Installing Express.js

To install Express, run:

npm install express

This adds Express as a dependency in the package.json file.

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4. Creating a Basic Express Server

Step 1: Create an index.js File

Inside the project folder, create a new file named index.js and open it in your editor.

Step 2: Add the Following Code

const express = require('express');  // Import Express
const app = express();  // Create an Express app

const PORT = 3000;  // Define the port

// Define a simple route
app.get('/', (req, res) => {
    res.send('Hello, World! Welcome to Express.js');
});

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

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5. Running the Express Server

Save the file and run the following command in the terminal:

node index.js

You should see this output:

Server is running on http://localhost:3000

Open your browser and go to http://localhost:3000. You should see the message “Hello, World! Welcome to Express.js” displayed.

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6. Understanding Routes in Express

Routes define how an application responds to client requests.

Adding More Routes

Modify index.js to include more routes:

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

app.get('/contact', (req, res) => {
    res.send('Contact us at: [email protected]');
});

Now, you can visit:

• http://localhost:3000/about → Displays “This is the About page”
• http://localhost:3000/contact → Displays “Contact us at: [email protected]“

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7. Handling Request Parameters and Query Strings

Route Parameters

Example of dynamic URL parameters:

app.get('/user/:name', (req, res) => {
    res.send(`Welcome, ${req.params.name}!`);
});

Visiting http://localhost:3000/user/John will display:

Welcome, John!

Query Strings

Access query parameters using req.query:

app.get('/search', (req, res) => {
    let query = req.query.q;
    res.send(`You searched for: ${query}`);
});

Visiting http://localhost:3000/search?q=express will display:

You searched for: express

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8. Using Middleware in Express

Logging Middleware

Create a simple logger middleware:

app.use((req, res, next) => {
    console.log(`Request Method: ${req.method}, Request URL: ${req.url}`);
    next();  // Move to the next middleware or route
});

Serving Static Files

To serve static files (like images, CSS, JavaScript), use express.static():

app.use(express.static('public'));

Create a public folder in your project and add a file like public/index.html.

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9. Handling Form Data in Express

To process form data, install body-parser:

npm install body-parser

Then, update index.js:

const bodyParser = require('body-parser');
app.use(bodyParser.urlencoded({ extended: true }));

app.post('/submit', (req, res) => {
    res.send(`Received data: ${req.body.name}`);
});

Now, posting data to /submit will process form inputs.

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10. Handling Errors in Express

Use a middleware function to handle errors:

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

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11. Using Nodemon for Auto-Restart

Install nodemon:

npm install -g nodemon

Run the server with:

nodemon index.js

Now, it automatically restarts on file changes.

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12. Deploying Your Express App

You can deploy on:

• Heroku
• Vercel
• Render
• DigitalOcean

Example steps for deploying on Heroku:

npm install -g heroku
heroku login
git init
heroku create
git add .
git commit -m "Deploy Express App"
git push heroku master

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Conclusion

Congratulations! 🎉 You’ve built a basic Express.js application, learned about routing, middleware, error handling, and deployment.

Next Steps

• Connect Express with MongoDB (using Mongoose).
• Implement JWT authentication.
• Build a REST API with Express & MongoDB.

Start experimenting and build something amazing with Express.js! 🚀