How to connect to MongoDB Atlas using Mongoose and Node

MongoDB Atlas is a fully managed service that has a fantastic free tier available for developers learning how to build document databases. MongoDB has a long-established history, is battle hardened, and is often used as part of the M.E.A.N (Mongo, Express, Angular, Node) stack (as well as other variants). There is no better time than now to learn and start using MongoDB in production environments to improve the performance of your web applications.

TL;DR All source code is available on GitHub.

Let’s get started.

How to create a database in MongoDB Atlas

Creating a database in MongoDB Atlas is fairly straight forward, so we will walk through some of those steps here.

Sign up with MongoDB

Head over to MongoDB Atlas or MLab and create a free account.

Accept the terms and conditions and go to the dashboard.

Create your first MongoDB cluster

A modal should appear asking you to build your first MongoDB cluster.

Click Build my first cluster.

Choose a cloud provider (we will be using AWS) and choose a free tier. At the time of writing, us-east-1 has a free service, which is indicated with a FREE TIER AVAILABLE tag.

Optionally, give your cluster a name and click Create Cluster at the bottom of the screen. It will take up to several minutes for your cluster to be created.

Create a Node.js project with Moogoose

This post will do the minimum possible required to get you up and running, whilst other posts will focus on more advanced functionality.

Create a new folder on your computer, called MongoAtlasNodeMongoose and open your terminal to that folder. Run the following command;

npm init -y

This will give you a package.json so we can add some dependencies.

Run the following command;

npm i --save mongoose

This will install Mongoose so we can refer to it from code.

Create a new file called index.js and add the following code;

const username = process.argv[2].split('=')[1]
console.log(`Hello, ${username}`)

This code retrieves a username passed in from the terminal (which you will see next). We will later use that by saving it to the database and retrieving it.

Run the following command;

node ./index.js --user=bob

You should see the following;

Hello, bob

We’re all set to wire up Mongoose and connect to our MongoDB Atlas database.

Use Mongoose to add and retrieve data from MongoDB Atlas database

To work with MongoDB, we need to define the shape of our data (the Schema), connect to the database, run our query and then close the connection, so let’s get started.

Define a User schema with Mongoose

Create a new file called userSchema.js and add the following;

const mongoose = require('mongoose')

const userSchema = new mongoose.Schema({
  username: {
    type: String,
    required: [true, 'Username is required']
  },
  created: {
    type: Date,
    required: [true, 'Created date is required']
  }
})

module.exports = userSchema

Let’s take a minute to analyse the schema;

• We use mongoose.Schema and pass an object for each field in our table
• We define the type of each field using built in JavaScript types
• We specify if the field is required, and the error to provide if the field is not provided
• We export the schema so it can be used later

We will import the schema shortly.

How to retrieve the connection string for your MongoDB Atlas database

Once your database has been created, on the Clusters dashboard you should be a Connect button. Click Connect and you should see the following modal;

There are a few steps here to retrieve your connection string.

• Whitelist your current IP address. Click Add your current IP address so that you can connect to your database remotely. MongoDB Atlas should recognise your IP and prefill it for you.
• Create a new MongoDB user. Set a username and password and make note of those of these as we will need them shortly. Click Create MongoDB User to finish the process.
• Click Choose a connection method, then click Connect Your Application.
• Choose **Standard Connection String (For drivers compatible with MongoDB 3.4+) and copy the connection string.

Go back to your Node application (index.js) and add the following line of code;

const connectionString = '<YOUR CONNECTION STRING HERE>'

Be sure to replace <PASSWORD> with the password you specified earlier.

How to connect to MongoDB Atlas using Node and Mongoose

All the pieces are in place, so let’s connect to the database, save some data, and then retrieve it based on what we pass as the user parameter in the terminal.

Remove all the code from index.js (except the connectionString) and add the following;

const mongoose = require('mongoose')
const userSchema = require('./userSchema.js')
const User = mongoose.model('user', userSchema, 'user')

async function createUser(username) {
  return new User({
    username,
    created: Date.now()
  }).save()
}

async function findUser(username) {
  return await User.findOne({ username })
}

;(async () => {
  const connector = mongoose.connect(connectionString)
  const username = process.argv[2].split('=')[1]

  let user = await connector.then(async () => {
    return findUser(username)
  })

  if (!user) {
    user = await createUser(username)
  }

  console.log(user)
  process.exit(0)
})()

And as before, let’s walk through this code to ensure we understand what it does;

• Tell Mongoose about our user model, and its schema
• We have a function called createUser, which accepts the username parameter passed in from the command line and uses it to create a new User entity with a Date which represents when the entity was created
• We have another function called findUser, which finds a single entity in the database whose username matches the username given to it (this prevents us from adding duplicate entries in the database!)
• We connect to MongoDB using the connectionString we defined earlier
• First, we attempt to find the user in the database, if the user does not exist, then we create it and log the user to the console.

Run the following command (several times if you like!);

node ./index.js --user=bob

A new user should be added to the database the first time your run the command. You will notice that MongoDB has conveniently added an _id property for us (so we do not have to generate our own!). If you run the same command you should see the exact same entity retrieved with the same _id.

➜  MongoAtlasNodeMongoose node ./index.js --user=bob
(node:80784) DeprecationWarning: current URL string parser is deprecated, and will be removed in a future version. To use the new parser, pass option { useNewUrlParser: true } to MongoClient.connect.
{ _id: 5c726f304a30a73b707814a0,
  username: 'bob',
  created: 2019-02-24T10:17:20.727Z,
  __v: 0 }

Congratulations, you have successfully connected to MongoDB Atlas using Mongoose and Node.js! You have also added data and then later retrieved it.

Summary

MongoDB Atlas has a generous free tier (512MB storage) which is perfect for getting started. Mongoose has an excellent API for defining schemas/models, connecting to the database and querying data. We learnt how to write a simple application to connect to MongoDB Atlas, create users and retrieve them.