**Course Title:** Mastering Node.js: Building Scalable Web Applications **Section Title:** Managing Data with MongoDB and Mongoose **Topic:** Defining Schemas and Models with Mongoose In this topic, we will explore the process of defining schemas and models with Mongoose, a popular Object Data Modeling (ODM) library for MongoDB and Node.js. By the end of this topic, you will be able to create robust and scalable data models for your MongoDB database using Mongoose. **What are Schemas and Models?** Before we dive into defining schemas and models with Mongoose, let's briefly discuss what they are. * **Schemas**: A schema is a blueprint or a definition of the structure of your data. It defines the fields, data types, and relationships between different data entities. * **Models**: A model is an instance of a schema. It represents a collection of data in your MongoDB database. **Defining Schemas with Mongoose** To define a schema with Mongoose, you need to create a new Mongoose model using the `mongoose.model()` method. Here's an example: ```javascript const mongoose = require('mongoose'); const userSchema = new mongoose.Schema({ name: String, email: String, age: Number }); const User = mongoose.model('User', userSchema); ``` In this example, we define a schema for a user document with three fields: `name`, `email`, and `age`. We then create a Mongoose model called `User` using the `mongoose.model()` method. **Defining Fields with Mongoose** When defining fields in a schema, you can specify the following properties: * **Type**: The data type of the field. Mongoose supports the following data types: `String`, `Number`, `Date`, `Buffer`, `Boolean`, `Mixed`, and `ObjectId`. * **Required**: A boolean indicating whether the field is required or not. * **Default**: The default value of the field. * **Min** and **Max**: The minimum and maximum values of the field. Here's an example: ```javascript const userSchema = new mongoose.Schema({ name: { type: String, required: true, default: 'John Doe' }, email: { type: String, required: true, min: 5, max: 50 }, age: { type: Number, required: true, min: 18, max: 100 } }); ``` **Defining Indexes with Mongoose** Indexes are used to improve the performance of queries on a field or a combination of fields. You can define indexes on a schema using the `index()` method. Here's an example: ```javascript const userSchema = new mongoose.Schema({ name: String, email: String, age: Number }); userSchema.index({ email: 1 }); ``` In this example, we define an index on the `email` field. **Defining Virtuals with Mongoose** Virtuals are fields that are not stored in the database but are computed on the fly. You can define virtuals on a schema using the `virtual()` method. Here's an example: ```javascript const userSchema = new mongoose.Schema({ name: String, email: String, age: Number }); userSchema.virtual('fullName').get(function() { return this.name + ' ' + this.lastName; }); ``` In this example, we define a virtual field called `fullName` that is computed by concatenating the `name` and `lastName` fields. **Conclusion** In this topic, we covered the process of defining schemas and models with Mongoose. We discussed the importance of schemas and models, how to define fields with Mongoose, how to define indexes with Mongoose, and how to define virtuals with Mongoose. By following the examples and explanations in this topic, you should be able to create robust and scalable data models for your MongoDB database using Mongoose. **What's Next?** In the next topic, we will explore how to perform CRUD (Create, Read, Update, Delete) operations with Mongoose. We will cover how to create, read, update, and delete documents in a MongoDB collection using Mongoose. **Leave a Comment or Ask for Help** If you have any questions or need help with any of the concepts covered in this topic, please leave a comment below. I'll do my best to assist you. **External Resources** For more information on Mongoose, please refer to the official Mongoose documentation: <https://mongoosejs.com/docs/> For more information on MongoDB, please refer to the official MongoDB documentation: <https://docs.mongodb.com/> For more information on Node.js, please refer to the official Node.js documentation: <https://nodejs.org/en/docs/>

const mongoose = require('mongoose');

const userSchema = new mongoose.Schema({
    name: String,
    email: String,
    age: Number
});

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

const userSchema = new mongoose.Schema({
    name: {
        type: String,
        required: true,
        default: 'John Doe'
    },
    email: {
        type: String,
        required: true,
        min: 5,
        max: 50
    },
    age: {
        type: Number,
        required: true,
        min: 18,
        max: 100
    }
});

const userSchema = new mongoose.Schema({
    name: String,
    email: String,
    age: Number
});

userSchema.index({ email: 1 });

const userSchema = new mongoose.Schema({
    name: String,
    email: String,
    age: Number
});

userSchema.virtual('fullName').get(function() {
    return this.name + ' ' + this.lastName;
});