using-mongoose.md

Use Mongodb using the Mongoose ODM

Mongoose is an ODM (Object Data Model) that provides a simple schema-based solution for modeling your application data. It includes built-in type casting, validation, query building, business logic hooks, and more, ready to use.

To start a project, we are going to create a folder and start a project with npm:

$ mkdir mongoose_app_test && cd mongoose_app_test

We start a project with npm

$ npm init -y

Install the Mongoose ODM

$ npm i --save mongoose

Import Mongoose to our project, create a file database.js, and add the following code

const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost:27017/example')

When we connect to MongoDB using the connect function, it accepts two optional parameters. The second parameter is an options object, where it can be specified as the username and password, if necessary. Finally, the third parameter is a function that returns the result after trying to connect to the database. It can be used in two ways

Example:

// Nomal
mongoose.connect(url, options, (err) => {
    if (err) throw err;
    console.log('Database Connected!');
});

// Promises

mongoose.connect(url, options).then(
    () => {/* Database Connected! */ },
    (err) => {/* Database Connection Error */}
});

Mongoose delivers an incredible amount of functionalities to create and work with schemes. Mongoose currently contains eight SchemaTypes that property keeps, like when you preserve a MongoDB. These are:

1. String
2. Number
3. Date
4. Buffer
5. Boolean
6. Mixed
7. ObjectId
8. Array

Define a Mongoose Scheme

To create a scheme we will use mongoose.Scheme() through the object mongoose, which will receive an object as an argument; for example:

We want to create a user with the properties name, email, and phone number; so we need to do the following to create that scheme:

Example 1:

const userSchema = mongoose.Schema({
    name: String,
    email: String,
    phone: String,
})

Example 2:

const userSchema = mongoose.Schema({
    _id: mongosee.Schema.Types.ObjectId,
    name: String,
    email: String,
    phone: String,
    created_at: {
        type: Date,
        default: Date.now
    }
})

Example 3:

const contactSchema = mongoose.Schema({
    _id: mongosee.Schema.Types.ObjectId,
    name: String,
    phone: String,
    user: {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'User'
    },
    created_at: {
        type: Date,
        default: Date.now
    }
})

Create the Mongoose Models

We previously created two schemes which are user and contact, which will help us to create the model's User and Contact respectively, using the mongoose.model() by means of the mongoose object.

Example 1:

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

Save data using the Mongoose Models

We previously created two schemes which are user and contact, which will help us to create users and contacts respectively in the database:

Example 1:

const user = new User({
    name: 'John Doe',
    email: '[email protected]',
    phone: '+1 555 555 55 55'
})

user.save((err) => {
    if(err) throw err;
    console.log('User created successfully!');
})

Select data using the Mongoose Models

We have previously inserted documents with the two models User and Contact, now the process to find is similar to create; only that we need to find the element we wish. To achieve that we have different methods like find(), findOne(), findById(), FindByIdAndUpdate():

Example 1:

const user = User.find({
    name: 'John Doe'
})

Example 2:

const contact = Contact.findById({
    _id: '632244bb405329d320cde2ae'
})

Update data using the Mongoose Models

Previously we have located documents with the User and Contact models, now the process to update is similar to create; only that we need to find the element we wish to update. To achieve that we have different methods such as update(), updateOne():

Example 1:

const user = User.find({
    name: 'John Doe'
})

user.update({ name: 'John A. Doe'}).exec((err) => {
    console.log("User updated!!!");
    mongoose.disconnect();
});

Example 2:

const contact = Contact.find({
    name: 'Jane Doe'
})

contact.updateOne({
    name: 'Jane M. Doe'
}).exec()

Delete documents using the Mongoose Models

We have previously updated documents with the User and Contact models, now the process to delete is similar to create or find, only that we need to find the element we wish to delete; or by using the model according to the supplied filter, for which we count with different methods such as deleteOne() deleteMany(); or using the instance of the document and using the delete method:

Ejemplo 1:

User.deleteOne({ name: 'John Doe' }, function (err) {
  if (err) throw err;
});

Example 2:

User.deleteMany({ is_active: false }, function (err) {
  if (err) throw err;
});