Mongoose count() Function

The Query.prototype.count() function is used to count the number of documents in a collection. This functions basically specifies this query as a count query.

Syntax:

Query.prototype.count()

Parameters: This function accepts one array parameter i.e. callback function.

Return Value: This function returns Query Object.

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

npm version mongoose

• After that, you can just create a folder and add a file for example, index.js as shown below.

Database: The sample database used here is shown below: 

Example 1: 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 }
});

var query = User.find();
query.count(function (err, count) {
    if (err) console.log(err)
    else console.log("Count is", count)
});

Steps to run the program:

• The project structure will look like this: 

• Run index.js file using below command: 

node index.js

Output:

Count is 4

Example 2: Filename: index.js

javascript

const express = require('express');
const mongoose = require('mongoose');
const app = express()

// 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 }
});

var query = User.find();
query.count(function (err, count) {
    if (err) console.log(err)
    else console.log("Count:", count)
});

app.listen(3000, function(error ) {
    if(error) console.log(error)
    console.log("Server listening on PORT 3000")
});

Steps to run the program:

• The project structure will look like this: 

• Run index.js file using below command: 

node index.js

Output:

Server listening on PORT 3000
Count: 4

Reference: https://mongoosejs.com/docs/api/query.html#query_Query-count