Mongoose Document Model.events API

The Model.events property of Mongoose API is used to return the model’s events instance. The instance of the event contains the fields like _events, _eventsCount, and _maxListeners.

Syntax:

Model_Name.events

Return Value: The Model.events property returns the events instance of the model.

Setting up Node.js application:

Step 1: Create a Node.js application using the following command:

npm init

Step 2: After creating the NodeJS application, Install the required module using the following command:

npm install mongoose

Project Structure: The project structure will look like this:

Example 1: In this example, we have established a database connection using mongoose and defined model over userSchema, having two columns or fields “name” and “age”. In the end, we are using the events property on the User model which will return the events instance of the model.

• app.js: Write down the below code in the app.js file:

Javascript

// Require mongoose module
const mongoose = require('mongoose');

// Set Up the Database connection
mongoose.connect(
    'mongodb://localhost:27017/geeksforgeeks', {
    useNewUrlParser: true,
    useUnifiedTopology: true
})

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

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

// Getting events property
const output = User.events
console.log("Events instance is:",output)

Steps to run the program: To run the application execute the below command from the root directory of the project:

node app.js

Output:

Events instance is: EventEmitter {
  _events: [Object: null prototype] {},
  _eventsCount: 0,
  _maxListeners: undefined,
  [Symbol(kCapture)]: false
}

Example 2: In this example, we have established a database connection using mongoose and defined model over studentSchema, having three columns or fields “name”, “father_name”, and “mother_name”. In the end, we are using events property on the Student model which will return events instance of the model with an event on it.

• app.js: Write down the below code in the app.js file:

Javascript

// Require mongoose module
const mongoose = require('mongoose');

// Set Up the Database connection
mongoose.connect(
'mongodb://localhost:27017/geeksforgeeks', {
useNewUrlParser: true,
useUnifiedTopology: true
})

const studentSchema = new mongoose.Schema(
{ name: String, father_name:
String, mother_name: String }
)

// Defining studentSchema model
const Student = mongoose.model('Student', studentSchema);

// Setting the events property
Student.events.on('error', err => console.log(err.message));

// Accessing base property on Student model
const output = Student.events
console.log("Events Instance is:", output)

Steps to run the program: To run the application execute the below command from the root directory of the project:

node app.js

Output:

Events Instance is: EventEmitter {
  _events: [Object: null prototype] { error: [Function (anonymous)] },
  _eventsCount: 1,
  _maxListeners: undefined,
  [Symbol(kCapture)]: false
}

Reference: https://mongoosejs.com/docs/api/model.html#model_Model-events