Connect to Azure Cosmos DB for NoSQL with the SDK

The Azure SDK for JavaScript (Node.js & Browser) is a suite of client libraries that provides a consistent developer interface to interact with many Azure services. Client libraries are packages that you would use to consume these resources and interact with them.

In this lab, you’ll connect to an Azure Cosmos DB for NoSQL account using the Azure SDK for JavaScript.

Prepare your development environment

If you have not already cloned the lab code repository for Build copilots with Azure Cosmos DB and set up your local environment, view the Setup local lab environment instructions to do so.

Create an Azure Cosmos DB for NoSQL account

If you already created an Azure Cosmos DB for NoSQL account for the Build copilots with Azure Cosmos DB labs on this site, you can use it for this lab and skip ahead to the next section. Otherwise, view the Setup Azure Cosmos DB instructions to create an Azure Cosmos DB for NoSQL account that you will use throughout the lab modules and grant your user identity access to manage data in the account by assigning it to the Cosmos DB Built-in Data Contributor role.

Import the @azure/cosmos library

The @azure/cosmos library is available on npm for easy installation into your JavaScript projects.

In Visual Studio Code, in the Explorer pane, browse to the javascript/01-sdk-connect folder.
Open the context menu for the javascript/01-sdk-connect folder and then select Open in Integrated Terminal to open a new terminal instance.

📝 This command will open the terminal with the starting directory already set to the javascript/01-sdk-connect folder.
Initialize a new Node.js project:
```
 npm init -y
```
Install the @azure/cosmos package using the following command:
```
 npm install @azure/cosmos
```
Install the @azure/identity library, which allows us to use Azure authentication to connect to the Azure Cosmos DB workspace, using the following command:
```
 npm install @azure/identity
```

Use the @azure/cosmos library

Once the Azure Cosmos DB library from the Azure SDK for JavaScript has been imported, you can immediately use its classes to connect to an Azure Cosmos DB for NoSQL account. The CosmosClient class is the core class used to make the initial connection to an Azure Cosmos DB for NoSQL account.

In Visual Studio Code, in the Explorer pane, browse to the javascript/01-sdk-connect folder.
Open the empty JavaScript file named script.js.

Add the following require statements to import the @azure/cosmos and @azure/identity libraries:

 const { CosmosClient } = require("@azure/cosmos");
 const { DefaultAzureCredential  } = require("@azure/identity");
 process.env.NODE_TLS_REJECT_UNAUTHORIZED = 0

Add variables named endpoint and credential and set the endpoint value to the endpoint of the Azure Cosmos DB account you created earlier. The credential variable should be set to a new instance of the DefaultAzureCredential class:
```
 const endpoint = "<cosmos-endpoint>";
 const credential = new DefaultAzureCredential();
```
📝 For example, if your endpoint is: https://dp420.documents.azure.com:443/, the statement would be: const endpoint = “https://dp420.documents.azure.com:443/”;.
Add a new variable named client and initialize it as a new instance of the CosmosClient class using the endpoint and credential variables:
```
 const client = new CosmosClient({ endpoint, aadCredentials: credential });
```

Add an async function named main to read and print account properties:

 async function main() {
     const { resource: account } = await client.getDatabaseAccount();
     console.log(`Consistency Policy: ${account.consistencyPolicy}`);
     console.log(`Primary Region: ${account.writableLocations[0].name}`);
 }

Invoke the main function:

 main().catch((error) => console.error(error));

Your script.js file should now look like this:

 const { CosmosClient } = require("@azure/cosmos");
 const { DefaultAzureCredential  } = require("@azure/identity");
 process.env.NODE_TLS_REJECT_UNAUTHORIZED = 0

 const endpoint = "<cosmos-endpoint>";
 const credential = new DefaultAzureCredential();

 const client = new CosmosClient({ endpoint, aadCredentials: credential });

 async function main() {
     const { resource: account } = await client.getDatabaseAccount();
     console.log(`Consistency Policy: ${account.consistencyPolicy}`);
     console.log(`Primary Region: ${account.writableLocations[0].name}`);
 }

 main().catch((error) => console.error(error));

Save the script.js file.

Test the script

Now that the JavaScript code to connect to the Azure Cosmos DB for NoSQL account is complete, you can test the script. This script will print the default consistency level and the name of the first writable region. When you created the account, you specified a location, and you should expect to see that same location value printed as the result of this script.

In Visual Studio Code, open the context menu for the javascript/01-sdk-connect folder and then select Open in Integrated Terminal to open a new terminal instance.
Before running the script, you must log into Azure using the az login command. At the terminal window, run:
```
 az login
```
Run the script using the node command:
```
 node script.js
```
The script will now output the default consistency level of the account and the first writable region. For example, if default consistency level for the account is Session, and the first writable region was East US, the script would output:
```
 Consistency Policy: Session
 Primary Region: East US
```
Close the integrated terminal.
Close Visual Studio Code.