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Ilyas Abdisalam
Ilyas Abdisalam

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✅ How to Use MongoDB with Express.js

#mongodb #express #webdev #programming

📘 Overview

This guide shows you how to connect a MongoDB database to an Express.js application using the official mongodb driver. This is useful for developers building full-stack JavaScript applications that need to store and retrieve data.

🧠 Prerequisites

Before you begin, make sure you have:

  • Node.js and npm installed
  • MongoDB installed locally or a MongoDB Atlas cloud database
  • Basic knowledge of JavaScript and Express.js

🛠️ Step 1: Create a New Express App

A. Create a new project folder:

mkdir express-mongo-app
cd express-mongo-app
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B. Initialize a Node.js project:

npm init -y
npm install express mongodb
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C. Create an index.js file with this boilerplate:

// CommonJS (used in Node.js by default, not ES6 module)
const express = require('express');
const app = express();
const port = 3000;

app.use(express.json());

app.listen(port, () => {
  console.log(`Server is running on http://localhost:${port}`);
});
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🔌 Step 2: Connect to MongoDB

A. At the top of index.js, import the MongoDB client:

const { MongoClient } = require('mongodb');
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B. Define your connection URL and database name:

const uri = 'mongodb://localhost:27017'; // Replace with your MongoDB Atlas URI if using cloud
const client = new MongoClient(uri);
const dbName = 'myDatabase';
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C. Create an async function to connect:

async function run() {
  try {
    await client.connect();
    console.log('Connected successfully to MongoDB');

    const db = client.db(dbName);
    const collection = db.collection('users');

    // Sample route to insert a user
    app.post('/users', async (req, res) => {
      const user = req.body;
      const result = await collection.insertOne(user);
      res.send(result);
    });

    // Sample route to get all users
    app.get('/users', async (req, res) => {
      const users = await collection.find({}).toArray();
      res.send(users);
    });

  } catch (err) {
    console.error(err);
  }
}

run();
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▶️ Step 3: Test the App

A. Start the server:

node index.js
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B. Use Postman or curl to test endpoints:

  • Insert a user: 
curl -X POST http://localhost:3000/users -H "Content-Type: application/json" -d '{"name": "Mohamed", "email": "[email protected]"}'
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  • Get all users: 
curl http://localhost:3000/users
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🧼 Step 4: Clean Up and Best Practices

  • Store your MongoDB URI in an environment variable (e.g., .env)
  • Handle connection errors and cleanup with process.on('SIGINT')
  • Use async/await consistently for clarity

✅ Summary

You’ve learned how to:

  • Set up a Node.js + Express.js app
  • Connect to MongoDB (local or Atlas)
  • Insert and retrieve data with API endpoints

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