Mongoose Plugins

Last Updated : 28 Apr, 2025

Plugins are a technique for reusing logic in multiple mongoose schemas. A plugin is similar to a method that you can use in your schema and reuse repeatedly over different instances of the schema. The main purpose of plugins is to modify your schemas. Plugins don't have anything to do with models or documents, so they can't execute queries or write to the database directly. A mongoose plugin is a JavaScript method that takes two parameters: the Schema, and an optional Options object.

Syntax:

function plugin_name(schema, options) {}

Parameters:

schema: Schema parameter lets you add to the particular schema. It is required.
options: Options parameter lets you define tunable parameters for your plugin. It is an optional parameter.

Installation of mongoose module:

Step 1: Create a folder and inside the terminal enter the following command to install node_modules.

npm init -y

Step 2: Install mongoose using the following command.

npm i mongoose

Step 3: After installing you can check the version using the following command.

npm info mongoose version

Step 4: After that create an index.js file and run it using the following command.

node index.js

We can add plugins in two ways to our schema.

Creating a custom plugins function
Installing an npm mongoose plugins package

Example 1: We want to create a plugin that can automatically save the creation timestamp

Step 1: Open a folder initialize the node project and install mongoose

npm init -y
npm i mongoose

Step 2: Then create the plugs.js file and add the below code:

plugs.js

JavaScript

module.exports = exports = 
function time_plugins(schema, options) {

    // Adding  created at and last access
    // date and time to the schema
    schema.add({ lastAccess: Date });
    schema.add({ createdAt: Date });
    
    // This will executed when save
    // function is called
    schema.pre('save', function (next) {
        this.createdAt = new Date()
        this.lastAccess = new Date();
        next()
    });

    // It will execute when find function
    // is called and update last access 
    // value to current date and time
    schema.post('find', async function (result) {
        if (result) {
            await this.updateMany({}, { 
                lastAccess: new Date() 
            }, ).clone();
        }
    });
}

Step 3. Then create app.js and add the below code.

app.js

JavaScript

const mongoose = require('mongoose');
const url = 'mongodb://127.0.0.1:27017/test';
const conn = mongoose.connect(url);
mongoose.set('strictQuery', false)

// User Schema
const userSchema = new mongoose.Schema({
    name: String,
    email: String,
    password: type: String
});
userSchema.plugin(require('./plugs'));

// Compile the schema into a model
const User = mongoose.model('User', userSchema);

// Save a new user to the database
const user = new User({
    name: 'Geeks for Geeks',
    email: '[email protected]',
    password: 'mongoose'
});
user.save();

// find functions
User.find();

Step 4. Run the code by writing the below command

node app.js

You can use any GUI tool or terminal to see the database like we have used the MongoDB compass GUI tool as shown below:

Output:

Example 2: In this example, we will use the mongoose.plugin() to add the plugins to all the schema in the database

Step 1: Just add the plugin in the mongoose.plugin() and it will be added to all the plugins as shown below.

app.js

JavaScript

const mongoose = require('mongoose');

const url = 'mongodb://127.0.0.1:27017/test';
const conn = mongoose.connect(url);

// This will add the plugin to all the schemas
mongoose.plugin("./plugs")
mongoose.set('strictQuery', false)
const userSchema = new mongoose.Schema({
    name: String,
    email: String,
    password: String
});

const booksSchema = new mongoose.Schema({
    name: String,
    author: String,
})

// Compile the schema into a model
const User = mongoose.model('User', userSchema);
const Book = mongoose.model('Book', bookSchema);

// Save a new user to the database
const user = new User({
    name: 'Geeks for Geeks',
    email: '[email protected]',
    password: 'mongoose'
});

const book = new Book({
    name: "Mongoose Guides",
    author: "Geeks"
});

user.save();
books.save();
User.find({}, function (err, docs) { });
Book.find({}, function (err, docs) { });

Step 2: Run the code using the following command

node app.js

Output:

As you can see both schemas has the same plugin functionality.

Example 3: In this example, we have the same database but instead we will use a mongoose plugin module mongoose-hidden

Mongoose-hidden plugin is used to hide properties you do not want to send to the client example password, keys, etc. It works with toJSON() and toObjects()

Step 1: Install the mongoose-hidden module using the below command.

npm i mongoose-hidden

Step 2: Add the mongoose-hidden plugin to the schema and specify the hidden property to true in the schema definition.

app.js

JavaScript

const mongoose = require('mongoose');

// Mongodb Connection URL
const url = 'mongodb://127.0.0.1:27017/test';
const conn = mongoose.connect(url, {}) //
console.log("MongoDB is Connected")

// Creates a Schema
const userSchema = new mongoose.Schema({
    name: String,
    email: String,

    // Specify the property to be hidden
    password: { 
        type: String, 
        hide: true 
    }
});

// Add a plugin to the schema
userSchema.plugin(require('mongoose-hidden')());

// Compile the schema into a model
const User = mongoose.model('User', userSchema);

// Save a new user to the database
const user = new User({
    name: 'Geeks for Geeks',
    email: '[email protected]',
    password: 'mongoose'
});
user.save();

// Print the data
console.log(user.toJSON())