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Using MongoDB with Mongoose

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In this section, we will explore how to use MongoDB with Mongoose in a Node.js application. Mongoose is an Object Data Modeling (ODM) library for MongoDB and Node.js. It provides a straightforward, schema-based solution to model your application data.

Table of Contents

  1. Introduction to MongoDB and Mongoose
  2. Setting Up MongoDB
  3. Installing Mongoose
  4. Connecting to MongoDB
  5. Defining Schemas and Models
  6. CRUD Operations
  7. Practical Exercises
  8. Summary

Introduction to MongoDB and Mongoose

What is MongoDB?

  • MongoDB is a NoSQL database that stores data in flexible, JSON-like documents. It is designed for scalability and high performance.
  • Key Features:
    • Document-oriented storage
    • Indexing
    • Replication
    • Load balancing
    • Aggregation

What is Mongoose?

  • Mongoose is an ODM library for MongoDB and Node.js. It provides a schema-based solution to model application data.
  • Key Features:
    • Schema definitions
    • Middleware (pre and post hooks)
    • Validation
    • Type casting
    • Query building

Setting Up MongoDB

  1. Install MongoDB:

  2. Start MongoDB:

    • Run the following command to start the MongoDB server: 
      mongod

Installing Mongoose

To use Mongoose in your Node.js application, you need to install it via npm.

npm install mongoose

Connecting to MongoDB

Create a new file app.js and add the following code to connect to MongoDB using Mongoose:

const mongoose = require('mongoose');

// Replace 'your_database_url' with your actual MongoDB connection string
const dbURL = 'mongodb://localhost:27017/mydatabase';

mongoose.connect(dbURL, { useNewUrlParser: true, useUnifiedTopology: true })
  .then(() => console.log('MongoDB connected...'))
  .catch(err => console.log(err));

Explanation:

  • mongoose.connect(): Connects to the MongoDB server.
  • useNewUrlParser and useUnifiedTopology: Options to handle deprecation warnings.

Defining Schemas and Models

Schema Definition

A schema defines the structure of the documents within a collection.

const Schema = mongoose.Schema;

const userSchema = new Schema({
  name: {
    type: String,
    required: true
  },
  email: {
    type: String,
    required: true,
    unique: true
  },
  age: {
    type: Number,
    min: 0
  }
});

Model Creation

A model is a compiled version of the schema, which provides an interface to interact with the database.

const User = mongoose.model('User', userSchema);

CRUD Operations

Create

const newUser = new User({
  name: 'John Doe',
  email: '[email protected]',
  age: 30
});

newUser.save()
  .then(user => console.log(user))
  .catch(err => console.log(err));

Read

User.find()
  .then(users => console.log(users))
  .catch(err => console.log(err));

Update

User.updateOne({ email: '[email protected]' }, { age: 31 })
  .then(result => console.log(result))
  .catch(err => console.log(err));

Delete

User.deleteOne({ email: '[email protected]' })
  .then(result => console.log(result))
  .catch(err => console.log(err));

Practical Exercises

Exercise 1: Create a New User

  1. Define a schema for a Product with fields: name, price, and category.
  2. Create a new product and save it to the database.

Solution:

const productSchema = new Schema({
  name: {
    type: String,
    required: true
  },
  price: {
    type: Number,
    required: true
  },
  category: {
    type: String,
    required: true
  }
});

const Product = mongoose.model('Product', productSchema);

const newProduct = new Product({
  name: 'Laptop',
  price: 999.99,
  category: 'Electronics'
});

newProduct.save()
  .then(product => console.log(product))
  .catch(err => console.log(err));

Exercise 2: Find All Users

  1. Write a query to find all users in the User collection.

Solution:

User.find()
  .then(users => console.log(users))
  .catch(err => console.log(err));

Summary

In this section, we covered:

  • The basics of MongoDB and Mongoose.
  • How to set up MongoDB and install Mongoose.
  • Connecting to MongoDB using Mongoose.
  • Defining schemas and models.
  • Performing CRUD operations.

By now, you should have a good understanding of how to use MongoDB with Mongoose in a Node.js application. In the next section, we will explore using SQL databases with Sequelize.

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