Get started with Azure Cosmos DB for MongoDB using JavaScript

Article
11/17/2022

APPLIES TO: MongoDB

This article shows you how to connect to Azure Cosmos DB for MongoDB using the native MongoDB npm package. Once connected, you can perform operations on databases, collections, and docs.

Note

The example code snippets are available on GitHub as a JavaScript project.

API for MongoDB reference documentation | MongoDB Package (npm)

Prerequisites

An Azure account with an active subscription. Create an account for free.
Node.js LTS
Azure Command-Line Interface (CLI) or Azure PowerShell
Azure Cosmos DB for MongoDB resource

Create a new JavaScript app

Create a new JavaScript application in an empty folder using your preferred terminal. Use the npm init command to begin the prompts to create the package.json file. Accept the defaults for the prompts.
```
npm init
```
Add the MongoDB npm package to the JavaScript project. Use the npm install package command specifying the name of the npm package. The dotenv package is used to read the environment variables from a .env file during local development.
```
npm install mongodb dotenv
```
To run the app, use a terminal to navigate to the application directory and run the application.
```
node index.js
```

Connect with MongoDB native driver to Azure Cosmos DB for MongoDB

To connect with the MongoDB native driver to Azure Cosmos DB, create an instance of the MongoClient class. This class is the starting point to perform all operations against databases.

The most common constructor for MongoClient has two parameters:

Parameter	Example value	Description
`url`	`COSMOS_CONNECTION_STRING` environment variable	API for MongoDB connection string to use for all requests
`options`	`{ssl: true, tls: true, }`	MongoDB Options for the connection.

Refer to the Troubleshooting guide for connection issues.

Get resource name

Create a shell variable for resourceGroupName.

# Variable for resource group name
resourceGroupName="msdocs-cosmos"

Use the az cosmosdb list command to retrieve the name of the first Azure Cosmos DB account in your resource group and store it in the accountName shell variable.

# Retrieve most recently created account name
accountName=$(
    az cosmosdb list \
        --resource-group $resourceGroupName \
        --query "[0].name" \
        --output tsv
)

Create a shell variable for RESOURCE_GROUP_NAME.

# Variable for resource group name
$RESOURCE_GROUP_NAME = "msdocs-cosmos"

Use the Get-AzCosmosDBAccountKey cmdlet to retrieve the name of the first Azure Cosmos DB account in your resource group and store it in the accountName shell variable.
```
# Get the name of the first Azure Cosmos DB account in your resource group
$ACCOUNT_NAME = (Get-AzCosmosDBAccount -ResourceGroupName $RESOURCE_GROUP_NAME)[0].Name
```

Retrieve your connection string

Find the API for MongoDB connection string from the list of connection strings for the account with the az cosmosdb keys list command.
```
az cosmosdb keys list --type connection-strings \
    --resource-group $resourceGroupName \
    --name $accountName 
```
Record the PRIMARY KEY values. You'll use these credentials later.

Find the CONNECTION STRING from the list of keys and connection strings for the account with the Get-AzCosmosDBAccountKey cmdlet.

$parameters = @{
    ResourceGroupName = $RESOURCE_GROUP_NAME
    Name = $ACCOUNT_NAME
    Type = "ConnectionStrings"
}    
Get-AzCosmosDBAccountKey @parameters |
    Select-Object -Property "Primary MongoDB Connection String"

Record the CONNECTION STRING value. You'll use these credentials later.

Configure environment variables

To use the CONNECTION STRING values within your code, set this value in the local environment running the application. To set the environment variable, use your preferred terminal to run the following commands:

$env:COSMOS_CONNECTION_STRING = "<cosmos-connection-string>"

export COSMOS_CONNECTION_STRING="<cosmos-connection-string>"

A .env file is a standard way to store environment variables in a project. Create a .env file in the root of your project. Add the following lines to the .env file:

COSMOS_CONNECTION_STRING="<cosmos-connection-string>"

Create MongoClient with connection string

Add dependencies to reference the MongoDB and DotEnv npm packages.

// Read .env file and set environment variables
require('dotenv').config();

// Use official mongodb driver to connect to the server
const { MongoClient } = require('mongodb');

Define a new instance of the MongoClient class using the constructor, and process.env. to use the connection string.

// New instance of MongoClient with connection string
// for Cosmos DB
const url = process.env.COSMOS_CONNECTION_STRING;
const client = new MongoClient(url);

// connect to the server
await client.connect();

// client options
const options = client.options
console.log(`Options:\n${Object.keys(options).map(key => `\t${key}: ${options[key]}\n`)}`);

For more information on different ways to create a MongoClient instance, see MongoDB NodeJS Driver Quick Start.

Close the MongoClient connection

When your application is finished with the connection, remember to close it. The .close() call should be after all database calls are made.

client.close()

Use MongoDB client classes with Azure Cosmos DB for API for MongoDB

Before you start building the application, let's look into the hierarchy of resources in Azure Cosmos DB. Azure Cosmos DB has a specific object model used to create and access resources. The Azure Cosmos DB creates resources in a hierarchy that consists of accounts, databases, collections, and docs.

Diagram of the Azure Cosmos DB DB hierarchy including accounts, databases, collections, and docs.

Each type of resource is represented by one or more associated JavaScript classes. Here's a list of the most common classes:

Class	Description
`MongoClient`	This class provides a client-side logical representation for the API for MongoDB layer on Azure Cosmos DB. The client object is used to configure and execute requests against the service.
`Db`	This class is a reference to a database that may, or may not, exist in the service yet. The database is validated server-side when you attempt to access it or perform an operation against it.
`Collection`	This class is a reference to a collection that also may not exist in the service yet. The collection is validated server-side when you attempt to work with it.

The following guides show you how to use each of these classes to build your application.

Guide:

Next steps

Now that you've connected to an API for MongoDB account, use the next guide to create and manage databases.

Create a database in Azure Cosmos DB for MongoDB using JavaScript

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