Mongoose SchemaType.prototype.set() API

The SchemaType.prototype.set() function of the Mongoose API is used to allow us to transform or manipulate data before it gets stored in MongoDB or before a query is executed

Syntax:

SchemaType.prototype.set()

Parameters: It accepts the following parameter as mentioned above and described below:

fn: It is a function that performs some operation on the data and returns the transformed value.

Return type: It returns the SchemaType object as a response.

Setting up Node.js Mongoose Module:

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

The below examples will demonstrate the Mongoose SchemaType.prototype.set() method.

Example 1: In this example, we will create a setter that will allow us to convert a name into uppercase before it gets stored in DB.

Javascript

const mongoose = require('mongoose') 
  
// Database connection 
mongoose.connect('mongodb://localhost:27017/query-helpers', 
    { 
        dbName: 'event_db', 
        useNewUrlParser: true, 
        useUnifiedTopology: true
    }, err => err ? console.log(err) 
        : console.log('Connected to database')); 
  
function toUpper(v) { 
    return v.toUpperCase(); 
} 
  
const personSchema = new mongoose.Schema({ 
    name: { 
        type: String, 
        set: toUpper 
    }, 
    age: { 
        type: Number, 
    } 
}); 
  
const personsArray = [ 
    { 
        name: 'Luffy', 
        age: 19 
    }, 
    { 
        name: 'Nami', 
        age: 30 
    }, 
    { 
        name: 'Zoro', 
        age: 35 
    } 
] 
  
const Person = mongoose.model('Person', personSchema); 
  
(async () => { 
    await Person.insertMany(personsArray); 
    const res = await Person.find(); 
  
    console.log({ res }); 
})()

Step to Run Application: Run the application using the following command from the root directory of the project:

node main.js

Output:

GUI Representation of the Database using MongoDB Compass:

Example 2: In this example, we will create a setter that will allow us to convert an age into a number before it gets stored in DB.

Javascript

const mongoose = require('mongoose') 
  
// Database connection 
mongoose.connect('mongodb://localhost:27017/query-helpers', 
    { 
        dbName: 'event_db', 
        useNewUrlParser: true, 
        useUnifiedTopology: true
    }, err => err ? console.log(err) 
        : console.log('Connected to database')); 
  
function helper(val) { 
    if (typeof val === 'string') { 
        val = Number(val) 
    } 
    return val; 
} 
  
  
const personSchema = new mongoose.Schema({ 
    name: { 
        type: String, 
    }, 
    age: { 
        type: Number, 
        set: helper 
    } 
}); 
  
const personsArray = [ 
    { 
        name: 'Luffy', 
        age: '19'
    }, 
    { 
        name: 'Nami', 
        age: '30'
    }, 
    { 
        name: 'Zoro', 
        age: '35'
    } 
] 
  
const Person = mongoose.model('Person', personSchema); 
  
(async () => { 
    await Person.insertMany(personsArray); 
    const res = await Person.find(); 
  
    console.log({ res }); 
})()

Step to Run Application: Run the application using the following command from the root directory of the project:

node main.js

Output:

GUI Representation of the Database using MongoDB Compass:

Reference: https://mongoosejs.com/docs/api/schematype.html#schematype_SchemaType-set

Javascript

Javascript

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