Mongoose Query prototype.where() API

Last Updated : 26 Apr, 2025

Mongoose is a MongoDB object modeling and handling for a node.js environment. Mongoose Query where() method is used to filter the documents from a collection using the MongoDB query system. It can be used in various ways, like chaining or passing query conditions. Let’s understand more about this with some examples.

Syntax:

Query.prototype.where()

Parameters: It accepts 2 parameters that are described below::

path: It is of type String or Object.
val: It can be of any type.

Return type: It returns the Query object.

Creating node application And Installing Mongoose:

Step 1: Create a node application using the following command:

mkdir folder_name
cd folder_name
npm init -y
touch main.js

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

npm install mongoose

Project Structure: It will look like the following.

GUI Representation of the Database using MongoDB Compass: Currently, the collection has no data.

Example 1: In this example, we will use Query where() method to filter out the documents using the chaining method where we would chain different queries together.

Filename: main.js

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')); 
  
const personSchema = new mongoose.Schema({ 
    name: { 
        type: String, 
    }, 
    age: { 
        type: Number, 
    } 
}); 
  
const personsArray = [ 
    { 
        name: 'John', 
        age: 22 
    }, 
    { 
        name: 'Dave', 
        age: 17 
    }, 
    { 
        name: 'Earl', 
        age: 12 
    } 
] 
  
const Person = mongoose.model('Person', personSchema); 
  
(async () => { 
    await Person.insertMany(personsArray); 
    const persons =  
        await Person.find().where('age').gte(18); 
    console.log(persons); 
})()

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

node main.js

Output: We see that the value remains unchanged in the result.

GUI Representation of the Database using MongoDB Compass:

Example 2: In this example, we will use Query API where() method to filter out the documents by passing query conditions as the argument to the where() method.

Filename: main.js

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')); 
  
const personSchema = new mongoose.Schema({ 
    name: { 
        type: String, 
    }, 
    age: { 
        type: Number, 
    } 
}); 
  
const personsArray = [ 
    { 
        name: 'John', 
        age: 22 
    }, 
    { 
        name: 'Dave', 
        age: 17 
    }, 
    { 
        name: 'Earl', 
        age: 12 
    } 
] 
  
const Person = mongoose.model('Person', personSchema); 
  
(async () => { 
    await Person.insertMany(personsArray); 
    const persons = await Person.find().where 
        ({ age: { $lte: 18 } }) 
    console.log(persons); 
})()