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Note

TheBuild from scratch option walks you step by step through the process of creating a new project, installing packages, writing the code, and running a basic console app. This approach is recommended if you want to understand all the details involved in creating an app that connects to Azure Blob Storage. If you prefer to automate deployment tasks and start with a completed project, chooseStart with a template.

Note

TheStart with a template option uses the Azure Developer CLI to automate deployment tasks and starts you off with a completed project. This approach is recommended if you want to explore the code as quickly as possible without going through the setup tasks. If you prefer step by step instructions to build the app, chooseBuild from scratch.

Get started with the Azure Blob Storage client library for Node.js to manage blobs and containers.

In this article, you follow steps to install the package and try out example code for basic tasks.

In this article, you use theAzure Developer CLI to deploy Azure resources and run a completed console app with just a few commands.

API reference |Library source code |Package (npm) |Samples

Prerequisites

Azure account with an active subscription -create an account for free
Azure Storage account -Create a storage account
Node.js LTS

Setting up

This section walks you through preparing a project to work with the Azure Blob Storage client library for Node.js.

Create the Node.js project

Create a JavaScript application namedblob-quickstart.

In a console window (such as cmd, PowerShell, or Bash), create a new directory for the project:
```
mkdir blob-quickstart
```
Switch to the newly createdblob-quickstart directory:
```
cd blob-quickstart
```
Create apackage.json file:
```
npm init -y
```
Open the project in Visual Studio Code:
```
code .
```

Install the packages

From the project directory, install the following packages using thenpm install command.

Install the Azure Storage npm package:
```
npm install @azure/storage-blob
```
Install the Azure Identity npm package for a passwordless connection:
```
npm install @azure/identity
```
Install other dependencies used in this quickstart:
```
npm install uuid dotenv
```

Set up the app framework

From the project directory:

Create a new file namedindex.js

Copy the following code into the file:

const { BlobServiceClient } = require("@azure/storage-blob");const { v1: uuidv1 } = require("uuid");require("dotenv").config();async function main() {  try {    console.log("Azure Blob storage v12 - JavaScript quickstart sample");    // Quick start code goes here  } catch (err) {    console.err(`Error: ${err.message}`);  }}main()  .then(() => console.log("Done"))  .catch((ex) => console.log(ex.message));

WithAzure Developer CLI installed, you can create a storage account and run the sample code with just a few commands. You can run the project in your local development environment, or in aDevContainer.

Initialize the Azure Developer CLI template and deploy resources

From an empty directory, follow these steps to initialize theazd template, create Azure resources, and get started with the code:

Clone the quickstart repository assets from GitHub and initialize the template locally:
```
azd init --template blob-storage-quickstart-nodejs
```
You'll be prompted for the following information:
- Environment name: This value is used as a prefix for all Azure resources created by Azure Developer CLI. The name must be unique across all Azure subscriptions and must be between 3 and 24 characters long. The name can contain numbers and lowercase letters only.
Sign in to Azure:
```
azd auth login
```
Provision and deploy the resources to Azure:
```
azd up
```
You'll be prompted for the following information:
- Subscription: The Azure subscription that your resources are deployed to.
- Location: The Azure region where your resources are deployed.
The deployment might take a few minutes to complete. The output from theazd up command includes the name of the newly created storage account, which you'll need later to run the code.

Run the sample code

At this point, the resources are deployed to Azure and the code is almost ready to run. Follow these steps to install packages, update the name of the storage account in the code, and run the sample console app:

Install packages: Navigate to the localblob-quickstart directory. Install packages for the Azure Blob Storage and Azure Identity client libraries, along with other packages used in the quickstart, using the following command:
```
npm install @azure/storage-blob @azure/identity uuid dotenv
```
Update the storage account name: In the localblob-quickstart directory, edit the file namedindex.js. Find the<storage-account-name> placeholder and replace it with the actual name of the storage account created by theazd up command. Save the changes.
Run the project: Execute the following command to run the app:
```
node index.js
```
Observe the output: This app creates a container and uploads a text string as a blob to the container. The example then lists the blobs in the container and downloads the blob and displays the blob contents. The app then deletes the container and all its blobs.

To learn more about how the sample code works, seeCode examples.

When you're finished testing the code, see theClean up resources section to delete the resources created by theazd up command.

Object model

Azure Blob storage is optimized for storing massive amounts of unstructured data. Unstructured data is data that doesn't adhere to a particular data model or definition, such as text or binary data. Blob storage offers three types of resources:

The storage account
A container in the storage account
A blob in the container

The following diagram shows the relationship between these resources.

Diagram of Blob storage architecture

Use the following JavaScript classes to interact with these resources:

BlobServiceClient: TheBlobServiceClient class allows you to manipulate Azure Storage resources and blob containers.
ContainerClient: TheContainerClient class allows you to manipulate Azure Storage containers and their blobs.
BlobClient: TheBlobClient class allows you to manipulate Azure Storage blobs.

Code examples

These example code snippets show you how to do the following tasks with the Azure Blob Storage client library for #"#authenticate-to-azure-and-authorize-access-to-blob-data" data-linktype="self-bookmark">Authenticate to Azure and authorize access to blob data

Create a container

Upload blobs to a container

List the blobs in a container

Download blobs

Delete a container

Sample code is also available onGitHub.

Note

The Azure Developer CLI template includes a file with sample code already in place. The following examples provide detail for each part of the sample code. The template implements the recommended passwordless authentication method, as described in theAuthenticate to Azure section. The connection string method is shown as an alternative, but isn't used in the template and isn't recommended for production code.

Authenticate to Azure and authorize access to blob data

Application requests to Azure Blob Storage must be authorized. Using theDefaultAzureCredential class provided by the Azure Identity client library is the recommended approach for implementing passwordless connections to Azure services in your code, including Blob Storage.

You can also authorize requests to Azure Blob Storage by using the account access key. However, this approach should be used with caution. Developers must be diligent to never expose the access key in an unsecure location. Anyone who has the access key is able to authorize requests against the storage account, and effectively has access to all the data.DefaultAzureCredential offers improved management and security benefits over the account key to allow passwordless authentication. Both options are demonstrated in the following example.

DefaultAzureCredential supports multiple authentication methods and determines which method should be used at runtime. This approach enables your app to use different authentication methods in different environments (local vs. production) without implementing environment-specific code.

The order and locations in whichDefaultAzureCredential looks for credentials can be found in theAzure Identity library overview.

For example, your app can authenticate using your Azure CLI sign-in credentials with when developing locally. Your app can then use amanaged identity once it's deployed to Azure. No code changes are required for this transition.

Assign roles to your Microsoft Entra user account

When developing locally, make sure that the user account that is accessing blob data has the correct permissions. You'll needStorage Blob Data Contributor to read and write blob data. To assign yourself this role, you'll need to be assigned theUser Access Administrator role, or another role that includes theMicrosoft.Authorization/roleAssignments/write action. You can assign Azure RBAC roles to a user using the Azure portal, Azure CLI, or Azure PowerShell. For more information about theStorage Blob Data Contributor role, seeStorage Blob Data Contributor. For more information about the available scopes for role assignments, seeUnderstand scope for Azure RBAC.

In this scenario, you'll assign permissions to your user account, scoped to the storage account, to follow thePrinciple of Least Privilege. This practice gives users only the minimum permissions needed and creates more secure production environments.

The following example will assign theStorage Blob Data Contributor role to your user account, which provides both read and write access to blob data in your storage account.

Important

In most cases it will take a minute or two for the role assignment to propagate in Azure, but in rare cases it may take up to eight minutes. If you receive authentication errors when you first run your code, wait a few moments and try again.

In the Azure portal, locate your storage account using the main search bar or left navigation.
On the storage account overview page, selectAccess control (IAM) from the left-hand menu.
On theAccess control (IAM) page, select theRole assignments tab.
Select+ Add from the top menu and thenAdd role assignment from the resulting drop-down menu.
Use the search box to filter the results to the desired role. For this example, search forStorage Blob Data Contributor and select the matching result and then chooseNext.
UnderAssign access to, selectUser, group, or service principal, and then choose+ Select members.
In the dialog, search for your Microsoft Entra username (usually youruser@domain email address) and then chooseSelect at the bottom of the dialog.
SelectReview + assign to go to the final page, and thenReview + assign again to complete the process.

To assign a role at the resource level using the Azure CLI, you first must retrieve the resource id using theaz storage account show command. You can filter the output properties using the--query parameter.

az storage account show --resource-group '<your-resource-group-name>' --name '<your-storage-account-name>' --query id

Copy the outputId from the preceding command. You can then assign roles using theaz role command of the Azure CLI.

az role assignment create --assignee "<user@domain>" \    --role "Storage Blob Data Contributor" \    --scope "<your-resource-id>"

To assign a role at the resource level using Azure PowerShell, you first must retrieve the resource ID using theGet-AzResource command.

Get-AzResource -ResourceGroupName "<yourResourceGroupname>" -Name "<yourStorageAccountName>"

Copy theId value from the preceding command output. You can then assign roles using theNew-AzRoleAssignment command in PowerShell.

New-AzRoleAssignment -SignInName <user@domain> `    -RoleDefinitionName "Storage Blob Data Contributor" `    -Scope <yourStorageAccountId>

Sign in and connect your app code to Azure using DefaultAzureCredential

You can authorize access to data in your storage account using the following steps:

Make sure you're authenticated with the same Microsoft Entra account you assigned the role to on your storage account. You can authenticate via the Azure CLI, Visual Studio Code, or Azure PowerShell.
Sign-in to Azure through the Azure CLI using the following command:
```
az login
```
Install the Azure CLI to work withDefaultAzureCredential through Visual Studio Code.
On the main menu of Visual Studio Code, navigate toTerminal > New Terminal.
Sign-in to Azure through the Azure CLI using the following command:
```
az login
```
Sign-in to Azure using PowerShell via the following command:
```
Connect-AzAccount
```
To useDefaultAzureCredential, make sure that the@azure\identity package isinstalled, and the class is imported:
```
const { DefaultAzureCredential } = require('@azure/identity');
```
Add this code inside thetry block. When the code runs on your local workstation,DefaultAzureCredential uses the developer credentials of the prioritized tool you're logged into to authenticate to Azure. Examples of these tools include Azure CLI or Visual Studio Code.
```
const accountName = process.env.AZURE_STORAGE_ACCOUNT_NAME;if (!accountName) throw Error('Azure Storage accountName not found');const blobServiceClient = new BlobServiceClient(  `https://${accountName}.blob.core.windows.net`,  new DefaultAzureCredential());
```
Make sure to update the storage account name,AZURE_STORAGE_ACCOUNT_NAME, in the.env file or your environment's variables. The storage account name can be found on the overview page of the Azure portal.
Note
When deployed to Azure, this same code can be used to authorize requests to Azure Storage from an application running in Azure. However, you'll need to enable managed identity on your app in Azure. Then configure your storage account to allow that managed identity to connect. For detailed instructions on configuring this connection between Azure services, see theAuth from Azure-hosted apps tutorial.

A connection string includes the storage account access key and uses it to authorize requests. Always be careful to never expose the keys in an unsecure location.

Note

To authorize data access with the storage account access key, you'll need permissions for the following Azure RBAC action:Microsoft.Storage/storageAccounts/listkeys/action. The least privileged built-in role with permissions for this action isReader and Data Access, but any role which includes this action will work.

Sign in to theAzure portal.
Locate your storage account.
In the storage account menu pane, underSecurity + networking, selectAccess keys. Here, you can view the account access keys and the complete connection string for each key.
In theAccess keys pane, selectShow keys.
In thekey1 section, locate theConnection string value. Select theCopy to clipboard icon to copy the connection string. You'll add the connection string value to an environment variable in the next section.

You can see the connection string for your storage account using theaz storage account show-connection-string command.

az storage account show-connection-string --name "<your-storage-account-name>"

You can assemble a connection string with PowerShell using theGet-AzStorageAccount andGet-AzStorageAccountKey commands.

$saName = "yourStorageAccountName"$rgName = "yourResourceGroupName"$sa = Get-AzStorageAccount -StorageAccountName $saName -ResourceGroupName $rgName$saKey = (Get-AzStorageAccountKey -ResourceGroupName $rgName -Name $saName)[0].Value'DefaultEndpointsProtocol=https;AccountName=' + $saName + ';AccountKey=' + $saKey + ';EndpointSuffix=core.windows.net'

Configure your storage connection string

After you copy the connection string, write it to a new environment variable on the local machine running the application. To set the environment variable, open a console window, and follow the instructions for your operating system. Replace<yourconnectionstring> with your actual connection string.

Windows:

setx AZURE_STORAGE_CONNECTION_STRING "<yourconnectionstring>"

After you add the environment variable in Windows, you must start a new instance of the command window.

Linux:

export AZURE_STORAGE_CONNECTION_STRING="<yourconnectionstring>"

.env file:

AZURE_STORAGE_CONNECTION_STRING="<yourconnectionstring>"

The following code retrieves the connection string for the storage account from the environment variable created earlier, and uses the connection string to construct a service client object.

Add this code inside thetry block:

const AZURE_STORAGE_CONNECTION_STRING =   process.env.AZURE_STORAGE_CONNECTION_STRING;if (!AZURE_STORAGE_CONNECTION_STRING) {  throw Error('Azure Storage Connection string not found');}// Create the BlobServiceClient object with connection stringconst blobServiceClient = BlobServiceClient.fromConnectionString(  AZURE_STORAGE_CONNECTION_STRING);

Important

The account access key should be used with caution. If your account access key is lost or accidentally placed in an insecure location, your service may become vulnerable. Anyone who has the access key is able to authorize requests against the storage account, and effectively has access to all the data.DefaultAzureCredential provides enhanced security features and benefits and is the recommended approach for managing authorization to Azure services.

Create a container

Create a new container in the storage account. The following code example takes aBlobServiceClient object and calls thegetContainerClient method to get a reference to a container. Then, the code calls thecreate method to actually create the container in your storage account.

Add this code to the end of thetry block:

// Create a unique name for the containerconst containerName = 'quickstart' + uuidv1();console.log('\nCreating container...');console.log('\t', containerName);// Get a reference to a containerconst containerClient = blobServiceClient.getContainerClient(containerName);// Create the containerconst createContainerResponse = await containerClient.create();console.log(  `Container was created successfully.\n\trequestId:${createContainerResponse.requestId}\n\tURL: ${containerClient.url}`);

To learn more about creating a container, and to explore more code samples, seeCreate a blob container with JavaScript.

Important

Container names must be lowercase. For more information about naming containers and blobs, seeNaming and Referencing Containers, Blobs, and Metadata.

Upload blobs to a container

Upload a blob to the container. The following code gets a reference to aBlockBlobClient object by calling thegetBlockBlobClient method on theContainerClient from theCreate a container section.

The code uploads the text string data to the blob by calling theupload method.

Add this code to the end of thetry block:

// Create a unique name for the blobconst blobName = 'quickstart' + uuidv1() + '.txt';// Get a block blob clientconst blockBlobClient = containerClient.getBlockBlobClient(blobName);// Display blob name and urlconsole.log(  `\nUploading to Azure storage as blob\n\tname: ${blobName}:\n\tURL: ${blockBlobClient.url}`);// Upload data to the blobconst data = 'Hello, World!';const uploadBlobResponse = await blockBlobClient.upload(data, data.length);console.log(  `Blob was uploaded successfully. requestId: ${uploadBlobResponse.requestId}`);

To learn more about uploading blobs, and to explore more code samples, seeUpload a blob with JavaScript.

List the blobs in a container

List the blobs in the container. The following code calls thelistBlobsFlat method. In this case, only one blob is in the container, so the listing operation returns just that one blob.

Add this code to the end of thetry block:

console.log('\nListing blobs...');// List the blob(s) in the container.for await (const blob of containerClient.listBlobsFlat()) {  // Get Blob Client from name, to get the URL  const tempBlockBlobClient = containerClient.getBlockBlobClient(blob.name);  // Display blob name and URL  console.log(    `\n\tname: ${blob.name}\n\tURL: ${tempBlockBlobClient.url}\n`  );}

To learn more about listing blobs, and to explore more code samples, seeList blobs with JavaScript.

Download blobs

Download the blob and display the contents. The following code calls thedownload method to download the blob.

Add this code to the end of thetry block:

// Get blob content from position 0 to the end// In Node.js, get downloaded data by accessing downloadBlockBlobResponse.readableStreamBody// In browsers, get downloaded data by accessing downloadBlockBlobResponse.blobBodyconst downloadBlockBlobResponse = await blockBlobClient.download(0);console.log('\nDownloaded blob content...');console.log(  '\t',  await streamToText(downloadBlockBlobResponse.readableStreamBody));

The following code converts a stream back into a string to display the contents.

Add this codeafter themain function:

// Convert stream to textasync function streamToText(readable) {  readable.setEncoding('utf8');  let data = '';  for await (const chunk of readable) {    data += chunk;  }  return data;}

To learn more about downloading blobs, and to explore more code samples, seeDownload a blob with JavaScript.

Delete a container

Delete the container and all blobs within the container. The following code cleans up the resources created by the app by removing the entire container using thedelete method.

Add this code to the end of thetry block:

// Delete containerconsole.log('\nDeleting container...');const deleteContainerResponse = await containerClient.delete();console.log(  'Container was deleted successfully. requestId: ',  deleteContainerResponse.requestId);

To learn more about deleting a container, and to explore more code samples, seeDelete and restore a blob container with JavaScript.

Run the code

From a Visual Studio Code terminal, run the app.

node index.js

The output of the app is similar to the following example:

Azure Blob storage - JavaScript quickstart sampleCreating container...    quickstart4a0780c0-fb72-11e9-b7b9-b387d3c488daUploading to Azure Storage as blob:    quickstart4a3128d0-fb72-11e9-b7b9-b387d3c488da.txtListing blobs...    quickstart4a3128d0-fb72-11e9-b7b9-b387d3c488da.txtDownloaded blob content...    Hello, World!Deleting container...Done

Step through the code in your debugger and check yourAzure portal throughout the process. Check to see that the container is being created. You can open the blob inside the container and view the contents.

Clean up resources

When you're done with this quickstart, delete theblob-quickstart directory.
If you're done using your Azure Storage resource, use theAzure CLI to remove the Storage resource.

When you're done with the quickstart, you can clean up the resources you created by running the following command:

azd down

You'll be prompted to confirm the deletion of the resources. Entery to confirm.

Next step

Azure Storage samples and developer guides for JavaScript and TypeScript

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Quickstart: Azure Blob Storage client library for Node.js

In this article

Prerequisites

Setting up

Create the Node.js project

Install the packages

Set up the app framework

Initialize the Azure Developer CLI template and deploy resources

Run the sample code

Object model

Code examples

Authenticate to Azure and authorize access to blob data

Assign roles to your Microsoft Entra user account

Sign in and connect your app code to Azure using DefaultAzureCredential

Configure your storage connection string

Create a container

Upload blobs to a container

List the blobs in a container

Download blobs

Delete a container

Run the code

Clean up resources

Next step

Feedback

Additional resources

In this article