Connecting with Node.js

This guide will walk you through connecting to a MongoDB database using Node.js and the official MongoDB Node.js driver. We'll cover installation, basic CRUD (Create, Read, Update, Delete) operations, and error handling.

1. Installation

1.1. Prerequisites

Make sure you have Node.js and npm (Node Package Manager) installed on your system. You can download them from the official Node.js website: https://nodejs.org/

1.2. Installing the MongoDB Node.js Driver

Open your terminal and navigate to your project directory. Then, install the MongoDB driver using npm:

npm install mongodb

This command will download and install the mongodb package, making it available for use in your Node.js project.

2. Connecting to MongoDB

2.1. Basic Connection

Here's how to establish a connection to your MongoDB database:

 const { MongoClient } = require('mongodb');

// Replace with your MongoDB connection string
const uri = "mongodb://localhost:27017/"; // Or your cloud connection string

const client = new MongoClient(uri);

async function run() {
  try {
    // Connect the client to the server (optional starting in v4.7)
    await client.connect();
    // Establish and verify connection
    await client.db("admin").command({ ping: 1 });
    console.log("Connected successfully to server");
  } finally {
    // Ensures that the client will close when you finish/error
    await client.close();
  }
}
run().catch(console.dir); 

Explanation:

• require('mongodb'): Imports the MongoDB driver.
• MongoClient: Creates a new MongoClient instance. Important: Replace mongodb://localhost:27017/ with your actual MongoDB connection string. This may involve specifying a username, password, and database name, especially for cloud-hosted MongoDB instances (e.g., MongoDB Atlas). A typical Atlas connection string looks like this: mongodb+srv://<username>:<password>@<cluster-address>/?retryWrites=true&w=majority.
• client.connect(): Attempts to connect to the MongoDB server. This is now an asynchronous operation.
• client.db("admin").command({ ping: 1 }): Sends a ping command to verify the connection. This ensures that the connection is live and responsive.
• client.close(): Closes the connection to the MongoDB server. This is crucial to release resources and prevent connection leaks. Always close the connection after you're done with your operations.

3. Basic CRUD Operations

Let's explore the fundamental CRUD (Create, Read, Update, Delete) operations using the MongoDB Node.js driver. We'll assume we're working with a collection named users within a database named mydatabase.

 const { MongoClient } = require('mongodb');

const uri = "mongodb://localhost:27017/"; // Replace with your connection string
const client = new MongoClient(uri);

async function run() {
  try {
    await client.connect();

    const db = client.db("mydatabase"); // Replace with your database name
    const usersCollection = db.collection("users"); // Replace with your collection name

    // **1. Create (Insert)**
    const insertResult = await usersCollection.insertOne({ name: "John Doe", age: 30 });
    console.log("Inserted document:", insertResult.insertedId);

    // **2. Read (Find)**
    const findResult = await usersCollection.findOne({ name: "John Doe" });
    console.log("Found document:", findResult);

    // **3. Update**
    const updateResult = await usersCollection.updateOne({ name: "John Doe" }, { $set: { age: 31 } });
    console.log("Updated documents:", updateResult.modifiedCount);

    // **4. Delete**
    const deleteResult = await usersCollection.deleteOne({ name: "John Doe" });
    console.log("Deleted documents:", deleteResult.deletedCount);


  } finally {
    await client.close();
  }
}

run().catch(console.dir); 

Explanation:

• db("mydatabase"): Specifies the database you want to work with.
• collection("users"): Specifies the collection within the database.
• insertOne(): Inserts a single document into the collection. insertResult.insertedId contains the ID of the newly inserted document.
• findOne(): Finds a single document that matches the specified query. In this case, it finds a document where the name field is "John Doe".
• updateOne(): Updates a single document that matches the specified query. The $set operator is used to update the age field. updateResult.modifiedCount represents the number of documents modified by the update operation.
• deleteOne(): Deletes a single document that matches the specified query. deleteResult.deletedCount represents the number of documents deleted.

4. Handling Connection Errors

It's essential to handle potential errors that might occur during the connection process. The following example demonstrates how to catch and handle connection errors:

 const { MongoClient } = require('mongodb');

const uri = "mongodb://localhost:27017/"; // Replace with your connection string
const client = new MongoClient(uri);

async function run() {
  try {
    await client.connect();
    console.log("Connected successfully to server");
  } catch (error) {
    console.error("Error connecting to MongoDB:", error);
  } finally {
    await client.close();
  }
}

run(); 

Explanation:

• The try...catch block surrounds the connection attempt.
• If an error occurs during client.connect(), the catch block will be executed.
• console.error() is used to log the error message to the console.