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Connecting to MongoDB

Imagine you have a giant filing cabinet where you store all your important documents. In the Node.js world, that filing cabinet is called a **database**. MongoDB is one of the most popular databases, and it works beautifully with Node.js.

What is MongoDB?

MongoDB is a NoSQL database that stores data in flexible, JSON-like documents. Instead of tables with rows and columns (like SQL databases), MongoDB uses **collections** and **documents**.

SQL TermMongoDB Term
DatabaseDatabase
TableCollection
RowDocument
ColumnField

Think of MongoDB as a digital filing cabinet where each document can have different fields – unlike SQL where every row must have the same columns.

Installing MongoDB Driver

To connect Node.js with MongoDB, we need the official MongoDB driver. Install it in your project:
npm install mongodb

Setting Up MongoDB

Before connecting, you need MongoDB installed and running. You can:

Connecting to MongoDB (Local)
const { MongoClient } = require('mongodb');

<!-- Connection URL – local MongoDB runs on port 27017 -->
const url = 'mongodb://localhost:27017';
const dbName = 'myapp';

const client = new MongoClient(url);

async function connectDB() {
  try {
    <!-- Connect to the MongoDB server -->
    await client.connect();
    console.log('Connected successfully to MongoDB');
    
    <!-- Get the database -->
    const db = client.db(dbName);
    
    <!-- Now you can work with collections -->
    const collection = db.collection('users');
    
    <!-- Example: insert a document -->
    const result = await collection.insertOne({ name: 'John', age: 30 });
    console.log('Inserted document:', result.insertedId);
    
    <!-- Close the connection when done -->
    await client.close();
  } catch (err) {
    console.error('Error connecting to MongoDB:', err);
  }
}

connectDB();

Connecting to MongoDB Atlas (Cloud)

If you're using MongoDB Atlas, the connection string will look different:
<!-- Format: mongodb+srv://username:password@cluster.mongodb.net/dbname -->
const url = 'mongodb+srv://myuser:mypassword@cluster0.abcde.mongodb.net/myapp';

Better: Using Connection Pool

In a real application, you don't want to connect and disconnect for every operation. Instead, you create a connection once and reuse it.
let db;

async function getDB() {
  if (db) return db;
  
  const client = new MongoClient(url);
  await client.connect();
  db = client.db(dbName);
  return db;
}

Two Minute Drill

  • MongoDB is a NoSQL database that stores data in JSON-like documents.
  • Install the official driver: `npm install mongodb`.
  • Connect using `MongoClient` with a connection URL.
  • Local MongoDB runs at `mongodb://localhost:27017`.
  • Atlas provides cloud MongoDB with a connection string.
  • In production, maintain a persistent connection (connection pool).
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