Mongoose | countDocuments() Function

The countDocuments() function is used to count the number of documents that match the filter in a database collection.

Installation of mongoose module:

• You can visit the link to Install mongoose module. You can install this package by using this command.

npm install mongoose

• After installing mongoose module, you can check your mongoose version in the command prompt using the command.

npm version mongoose

• After that, you can just create a folder and add a file, for example, index.js. To run this file you need to run the following command.

node index.js

Filename: index.js

Javascript

const mongoose = require('mongoose');

// Database Connection
mongoose.connect('mongodb://127.0.0.1:27017/geeksforgeeks', {
    useNewUrlParser: true,
    useCreateIndex: true,
    useUnifiedTopology: true
});

// User model
const User = mongoose.model('User', {
    name: { type: String },
    age: { type: Number }
});

User.countDocuments({age:{$gte:5}}, function (err, count) {
    if (err){
        console.log(err)
    }else{
        console.log("Count :", count)
    }
});

Steps to run the program:

• The project structure will look like this:

• Make sure you have installed mongoose module using the following command:

npm install mongoose

• Below is the sample data in the database before the function is executed. You can use any GUI tool or terminal to see the database like we have used Robo3T GUI tool as shown below: 
  

• Run index.js file using below command:

node index.js

So this is how you can use the mongoose countDocuments() function which function counts a number of documents matching filter in a database collection.