Lecture 420:- Linking our MongoDB using Mongoose

Linking MongoDB using Mongoose in a Node.js application allows you to interact with the MongoDB database using a schema-based approach. Mongoose is an Object Data Modeling (ODM) library for MongoDB and provides a straightforward way to define data models and perform CRUD (Create, Read, Update, Delete) operations on the database.

To link MongoDB using Mongoose, follow these steps:

Step 1: Install Required Dependencies Make sure you have Node.js and npm installed. In your project directory, install the necessary packages: mongoose and dotenv.

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npm install mongoose dotenv

Step 2: Set Up Environment Variables Create a .env file in your project's root directory to store your MongoDB connection URI. Replace <YOUR_MONGODB_URI> with your actual MongoDB connection string. You can get this connection string from your MongoDB Atlas dashboard or your local MongoDB setup.

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MONGODB_URI=<YOUR_MONGODB_URI>

Step 3: Configure MongoDB Connection In your main application file (e.g., app.js), set up the MongoDB connection using Mongoose.

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// app.js require('dotenv').config(); const mongoose = require('mongoose'); const mongodbURI = process.env.MONGODB_URI; // Connect to MongoDB mongoose.connect(mongodbURI, {  useNewUrlParser: true,  useUnifiedTopology: true,  useCreateIndex: true,  useFindAndModify: false, }); // Check if the connection is successful const db = mongoose.connection; db.on('error', console.error.bind(console, 'MongoDB connection error:')); db.once('open', () => {  console.log('Connected to MongoDB successfully!'); }); // Your other application code goes here

Step 4: Define Mongoose Models In Mongoose, models are defined using schemas. A schema is a blueprint for your data model, defining the fields and their types for the documents in the MongoDB collection.

For example, let's create a simple User model:

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// models/User.js const mongoose = require('mongoose'); const userSchema = new mongoose.Schema({  username: {    type: String,    required: true,    unique: true,  },  email: {    type: String,    required: true,    unique: true,  },  age: {    type: Number,    required: true,  }, }); const User = mongoose.model('User', userSchema); module.exports = User;

Step 5: Using Mongoose Models Now that you have defined your Mongoose models, you can use them to perform CRUD operations on the MongoDB database.

For example, let's create and save a new user:

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// app.js const express = require('express'); const app = express(); const User = require('./models/User'); // Your other middleware and route handlers go here // Create a new user and save it to the database app.post('/create-user', async (req, res) => {  try {    const newUser = new User({      username: 'john_doe',      email: 'john@example.com',      age: 30,    });    const savedUser = await newUser.save();    res.json(savedUser);  } catch (err) {    res.status(500).json({ error: 'Failed to create user.' });  } }); // Start the server const port = 3000; app.listen(port, () => {  console.log(`Server is running on http://localhost:${port}`); });

Step 6: Test the MongoDB Connection Run your Node.js application using the following command:

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node app.js

If everything is set up correctly, your application should connect to MongoDB, and you should see the "Connected to MongoDB successfully!" message in the console.

Congratulations! You have now linked MongoDB using Mongoose in your Node.js application. You can now perform database operations using the defined Mongoose models, making it easy to work with MongoDB in a structured and schema-based manner.