Building a URL Shortener App with Node.js and MongoDB

Creating a URL shortener service is a great way to dive into full-stack development with Node.js and MongoDB. In this blog, we'll walk through the process of building a URL shortener application, which allows users to convert long URLs into shortened versions and track their usage.

Prerequisites

To follow this tutorial, you should have:

Node.js installed
Basic knowledge of JavaScript and Express.js
A MongoDB database (you can use MongoDB Atlas for a cloud solution)

Project Setup

Step 1: Initialize the Project

First, create a new directory for your project and initialize it with npm:

mkdir url-shortener-app
cd url-shortener-app
npm init -y

Step 2: Install Dependencies

Next, install the necessary dependencies:

npm install express mongoose cors dotenv
npm install --save-dev nodemon

Step 3: Project Structure

Create the following folder structure:

url-shortener-app/
├── controllers/
│   └── urlController.js
├── models/
│   └── urlModel.js
├── routes/
│   └── urlRoutes.js
├── .env
├── index.js
├── package.json

Building the Backend

Step 4: Set Up Express Server

In the index.js file, set up the Express server and connect to MongoDB:

const express = require('express');
const mongoose = require('mongoose');
const urlRoutes = require('./routes/urlRoutes');
const cors = require('cors');

const app = express();
app.use(express.json());

require("dotenv").config();

const dbUser = process.env.MONGODB_USER;
const dbPassword = process.env.MONGODB_PASSWORD;

// Connect to MongoDB
mongoose
    .connect(
        `mongodb+srv://${dbUser}:${dbPassword}@cluster0.re3ha3x.mongodb.net/url-shortener-app`,
        { useNewUrlParser: true, useUnifiedTopology: true }
    )
    .then(() => {
        console.log("Connected to MongoDB database!");
    })
    .catch((error) => {
        console.error("Connection failed!", error);
    });

app.use(cors({
    origin: "*",
}));

app.get('/', (req, res) => {
    res.send('Welcome to URL Shortener API');
});

app.use('/api', urlRoutes);

const PORT = process.env.PORT || 5000;
app.listen(PORT, () => {
    console.log(`Server is running on port ${PORT}`);
});

Create a .env file in the root directory to store environment variables:

MONGODB_USER=yourMongoDBUsername
MONGODB_PASSWORD=yourMongoDBPassword

Step 5: Define the URL Model

In the models/urlModel.js file, define the schema for URLs:

const mongoose = require('mongoose');

const urlSchema = new mongoose.Schema({
    originalUrl: { type: String, required: true },
    shortUrl: { type: String, required: true, unique: true },
    clicks: { type: Number, default: 0 },
    expirationDate: { type: Date },
    createdAt: { type: Date, default: Date.now },
});

module.exports = mongoose.model('Url', urlSchema);

Step 6: Create Routes

In the routes/urlRoutes.js file, define the routes for the API:

const express = require('express');
const { createShortUrl, redirectUrl, getUrls, getDetails, deleteUrl } = require('../controllers/urlController');
const router = express.Router();

router.post('/shorten', createShortUrl);
router.get('/urls', getUrls);
router.get('/:shortUrl', redirectUrl);
router.get('/details/:shortUrl', getDetails);
router.delete('/delete/:shortUrl', deleteUrl);

module.exports = router;

Step 7: Implement Controllers

In the controllers/urlController.js file, implement the controller functions:

const Url = require('../models/urlModel');

function generateUniqueId(length) {
    const characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
    let result = '';
    for (let i = 0; i < length; i++) {
        const randomIndex = Math.floor(Math.random() * characters.length);
        result += characters[randomIndex];
    }
    return result;
}

const createShortUrl = async (req, res) => {
    const { originalUrl } = req.body;
    const shortUrl = generateUniqueId(5);
    const urlRegex = new RegExp(/^(http|https):\/\/[^ "]+$/);
    if (!urlRegex.test(originalUrl))
        return res.status(400).json('Invalid URL');
    const url = await Url.findOne({ originalUrl });
    if (url) {
        res.json(url);
        return;
    }
    const expirationDate = new Date();
    expirationDate.setDate(expirationDate.getDate() + 7);
    const newUrl = new Url({ originalUrl, shortUrl, expirationDate });
    await newUrl.save();
    res.json(newUrl);
};

const redirectUrl = async (req, res) => {
    const { shortUrl } = req.params;
    const url = await Url.findOne({ shortUrl });
    if (!url || (url.expirationDate && url.expirationDate < new Date())) {
        res.status(404).json('URL expired or not found');
        return;
    }
    url.clicks++;
    await url.save();
    res.redirect(url.originalUrl);
};

const getUrls = async (req, res) => {
    try {
        const urls = await Url.find({}).sort({ _id: -1 });
        res.json(urls);
    } catch (error) {
        res.status(500).json({ message: 'Server Error' });
    }
};

const getDetails = async (req, res) => {
    try {
        const { shortUrl } = req.params;
        const url = await Url.findOne({ shortUrl });
        if (url) {
            res.json(url);
        } else {
            res.status(404).json('URL not found');
        }
    } catch (error) {
        res.status(500).json({ message: 'Server Error' });
    }
};

const deleteUrl = async (req, res) => {
    try {
        const { shortUrl } = req.params;
        await Url.findOneAndDelete({ shortUrl });
        res.json('URL deleted');
    } catch (error) {
        res.status(500).json({ message: 'Server Error' });
    }
};

module.exports = { createShortUrl, redirectUrl, getDetails, getUrls, deleteUrl };

Running the Application

Start the server using the following command:

npm run dev

This command will start your server with Nodemon, which will automatically restart the server when you make changes to your code.

Conclusion

In this blog, we've built a simple URL shortener application using Node.js and MongoDB. This application allows users to shorten URLs, track their usage, and manage them with expiration dates. This project is a great starting point for learning about full-stack development and can be expanded with additional features such as user authentication, custom URL aliases, and more.