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--- title: Get started with Azure Service Bus topics (JavaScript) description: This tutorial shows you how to send messages to Azure Service Bus topics and receive messages from topics' subscriptions using the JavaScript programming language. author: spelluru ms.author: spelluru ms.date: 12/08/2023 ms.topic: quickstart ms.devlang: javascript ms.custom: - devx-track-js - mode-api - sfi-ropc-nochange --- # Send messages to an Azure Service Bus topic and receive messages from subscriptions to the topic (JavaScript) > [!div class="op_single_selector" title1="Select the programming language:"] > * [C#](service-bus-dotnet-how-to-use-topics-subscriptions.md) > * [Java](service-bus-java-how-to-use-topics-subscriptions.md) > * [JavaScript](service-bus-nodejs-how-to-use-topics-subscriptions.md) > * [Python](service-bus-python-how-to-use-topics-subscriptions.md) In this tutorial, you complete the following steps: 1. Create a Service Bus namespace, using the Azure portal. 2. Create a Service Bus topic, using the Azure portal. 3. Create a Service Bus subscription to that topic, using the Azure portal. 4. Write a JavaScript application to use the [@azure/service-bus](https://www.npmjs.com/package/@azure/service-bus) package to: * Send a set of messages to the topic. * Receive those messages from the subscription. > [!NOTE] > This quick start provides step-by-step instructions for a simple scenario of sending a batch of messages to a Service Bus topic and receiving those messages from a subscription of the topic. You can find pre-built JavaScript and TypeScript samples for Azure Service Bus in the [Azure SDK for JavaScript repository on GitHub](https://github.com/Azure/azure-sdk-for-js/tree/main/sdk/servicebus/service-bus/samples/v7). ## Prerequisites - An Azure subscription. To complete this tutorial, you need an Azure account. You can activate your [MSDN subscriber benefits](https://azure.microsoft.com/pricing/member-offers/credit-for-visual-studio-subscribers/?WT.mc_id=A85619ABF) or sign up for a [free account](https://azure.microsoft.com/pricing/purchase-options/azure-account?cid=msft_learn). - [Node.js LTS](https://nodejs.org/en/download/package-manager/) - Follow steps in the [Quickstart: Use the Azure portal to create a Service Bus topic and subscriptions to the topic](service-bus-quickstart-topics-subscriptions-portal.md). You will use only one subscription for this quickstart. ### [Passwordless](#tab/passwordless) To use this quickstart with your own Azure account, you need: * Install [Azure CLI](/cli/azure/install-azure-cli), which provides the passwordless authentication to your developer machine. * Sign in with your Azure account at the terminal or command prompt with `az login`. * Use the same account when you add the appropriate role to your resource. * Run the code in the same terminal or command prompt. * Note down your **topic** name and **subscription** for your Service Bus namespace. You'll need that in the code. ### [Connection string](#tab/connection-string) Note down the following, which you'll use in the code below: * Service Bus namespace **connection string** * Service Bus namespace **topic** name you created * Service Bus namespace **subscription** --- > [!NOTE] > - This tutorial works with samples that you can copy and run using [Nodejs](https://nodejs.org/). For instructions on how to create a Node.js application, see [Create and deploy a Node.js application to an Azure Website](../app-service/quickstart-nodejs.md), or [Node.js Cloud Service using Windows PowerShell](../cloud-services/cloud-services-nodejs-develop-deploy-app.md). [!INCLUDE [service-bus-create-namespace-portal](./includes/service-bus-create-namespace-portal.md)] [!INCLUDE [service-bus-create-topic-subscription-portal](./includes/service-bus-create-topic-subscription-portal.md)] [!INCLUDE [service-bus-passwordless-template-tabbed](../../includes/passwordless/service-bus/service-bus-passwordless-template-tabbed.md)] ## Use Node Package Manager (NPM) to install the package ### [Passwordless](#tab/passwordless) 1. To install the required npm package(s) for Service Bus, open a command prompt that has `npm` in its path, change the directory to the folder where you want to have your samples and then run this command. 1. Install the following packages: ```bash npm install @azure/service-bus @azure/identity ``` ### [Connection string](#tab/connection-string) 1. To install the required npm package(s) for Service Bus, open a command prompt that has `npm` in its path, change the directory to the folder where you want to have your samples and then run this command. 1. Install the following package: ```bash npm install @azure/service-bus ``` --- ## Send messages to a topic The following sample code shows you how to send a batch of messages to a Service Bus topic. See code comments for details. ### [Passwordless](#tab/passwordless) You must have signed in with the Azure CLI's `az login` in order for your local machine to provide the passwordless authentication required in this code. 1. Open your favorite editor, such as [Visual Studio Code](https://code.visualstudio.com/) 2. Create a file called `sendtotopic.js` and paste the below code into it. This code will send a message to your topic. > [!IMPORTANT] > The passwordless credential is provided with the [**DefaultAzureCredential**](https://github.com/Azure/azure-sdk-for-js/tree/main/sdk/identity/identity#defaultazurecredential). ```javascript const { ServiceBusClient } = require("@azure/service-bus"); const { DefaultAzureCredential } = require("@azure/identity"); // Replace `<SERVICE-BUS-NAMESPACE>` with your namespace const fullyQualifiedNamespace = "<SERVICE-BUS-NAMESPACE>.servicebus.windows.net"; // Passwordless credential const credential = new DefaultAzureCredential(); const topicName = "<TOPIC NAME>"; const messages = [ { body: "Albert Einstein" }, { body: "Werner Heisenberg" }, { body: "Marie Curie" }, { body: "Steven Hawking" }, { body: "Isaac Newton" }, { body: "Niels Bohr" }, { body: "Michael Faraday" }, { body: "Galileo Galilei" }, { body: "Johannes Kepler" }, { body: "Nikolaus Kopernikus" } ]; async function main() { // create a Service Bus client using the passwordless authentication to the Service Bus namespace const sbClient = new ServiceBusClient(fullyQualifiedNamespace, credential); // createSender() can also be used to create a sender for a queue. const sender = sbClient.createSender(topicName); try { // Tries to send all messages in a single batch. // Will fail if the messages cannot fit in a batch. // await sender.sendMessages(messages); // create a batch object let batch = await sender.createMessageBatch(); for (let i = 0; i < messages.length; i++) { // for each message in the array // try to add the message to the batch if (!batch.tryAddMessage(messages[i])) { // if it fails to add the message to the current batch // send the current batch as it is full await sender.sendMessages(batch); // then, create a new batch batch = await sender.createMessageBatch(); // now, add the message failed to be added to the previous batch to this batch if (!batch.tryAddMessage(messages[i])) { // if it still can't be added to the batch, the message is probably too big to fit in a batch throw new Error("Message too big to fit in a batch"); } } } // Send the last created batch of messages to the topic await sender.sendMessages(batch); console.log(`Sent a batch of messages to the topic: ${topicName}`); // Close the sender await sender.close(); } finally { await sbClient.close(); } } // call the main function main().catch((err) => { console.log("Error occurred: ", err); process.exit(1); }); ``` 3. Replace `<SERVICE BUS NAMESPACE CONNECTION STRING>` with the connection string to your Service Bus namespace. 1. Replace `<TOPIC NAME>` with the name of the topic. 1. Then run the command in a command prompt to execute this file. ```console node sendtotopic.js ``` 1. You should see the following output. ```console Sent a batch of messages to the topic: mytopic ``` ### [Connection string](#tab/connection-string) 1. Open your favorite editor, such as [Visual Studio Code](https://code.visualstudio.com/) 2. Create a file called `sendtotopic.js` and paste the below code into it. This code will send a message to your topic. ```javascript const { ServiceBusClient } = require("@azure/service-bus"); const connectionString = "<SERVICE BUS NAMESPACE CONNECTION STRING>" const topicName = "<TOPIC NAME>"; const messages = [ { body: "Albert Einstein" }, { body: "Werner Heisenberg" }, { body: "Marie Curie" }, { body: "Steven Hawking" }, { body: "Isaac Newton" }, { body: "Niels Bohr" }, { body: "Michael Faraday" }, { body: "Galileo Galilei" }, { body: "Johannes Kepler" }, { body: "Nikolaus Kopernikus" } ]; async function main() { // create a Service Bus client using the connection string to the Service Bus namespace const sbClient = new ServiceBusClient(connectionString); // createSender() can also be used to create a sender for a queue. const sender = sbClient.createSender(topicName); try { // Tries to send all messages in a single batch. // Will fail if the messages cannot fit in a batch. // await sender.sendMessages(messages); // create a batch object let batch = await sender.createMessageBatch(); for (let i = 0; i < messages.length; i++) { // for each message in the array // try to add the message to the batch if (!batch.tryAddMessage(messages[i])) { // if it fails to add the message to the current batch // send the current batch as it is full await sender.sendMessages(batch); // then, create a new batch batch = await sender.createMessageBatch(); // now, add the message failed to be added to the previous batch to this batch if (!batch.tryAddMessage(messages[i])) { // if it still can't be added to the batch, the message is probably too big to fit in a batch throw new Error("Message too big to fit in a batch"); } } } // Send the last created batch of messages to the topic await sender.sendMessages(batch); console.log(`Sent a batch of messages to the topic: ${topicName}`); // Close the sender await sender.close(); } finally { await sbClient.close(); } } // call the main function main().catch((err) => { console.log("Error occurred: ", err); process.exit(1); }); ``` 3. Replace `<SERVICE BUS NAMESPACE CONNECTION STRING>` with the connection string to your Service Bus namespace. 1. Replace `<TOPIC NAME>` with the name of the topic. 1. Then run the command in a command prompt to execute this file. ```console node sendtotopic.js ``` 1. You should see the following output. ```console Sent a batch of messages to the topic: mytopic ``` --- ## Receive messages from a subscription ### [Passwordless](#tab/passwordless) You must have signed in with the Azure CLI's `az login` in order for your local machine to provide the passwordless authentication required in this code. 1. Open your favorite editor, such as [Visual Studio Code](https://code.visualstudio.com/) 2. Create a file called **receivefromsubscription.js** and paste the following code into it. See code comments for details. ```javascript const { delay, ServiceBusClient, ServiceBusMessage } = require("@azure/service-bus"); const { DefaultAzureCredential } = require("@azure/identity"); // Replace `<SERVICE-BUS-NAMESPACE>` with your namespace const fullyQualifiedNamespace = "<SERVICE-BUS-NAMESPACE>.servicebus.windows.net"; // Passwordless credential const credential = new DefaultAzureCredential(); const topicName = "<TOPIC NAME>"; const subscriptionName = "<SUBSCRIPTION NAME>"; async function main() { // create a Service Bus client using the passwordless authentication to the Service Bus namespace const sbClient = new ServiceBusClient(fullyQualifiedNamespace, credential); // createReceiver() can also be used to create a receiver for a queue. const receiver = sbClient.createReceiver(topicName, subscriptionName); // function to handle messages const myMessageHandler = async (messageReceived) => { console.log(`Received message: ${messageReceived.body}`); }; // function to handle any errors const myErrorHandler = async (error) => { console.log(error); }; // subscribe and specify the message and error handlers receiver.subscribe({ processMessage: myMessageHandler, processError: myErrorHandler }); // Waiting long enough before closing the sender to send messages await delay(5000); await receiver.close(); await sbClient.close(); } // call the main function main().catch((err) => { console.log("Error occurred: ", err); process.exit(1); }); ``` 3. Replace `<SERVICE BUS NAMESPACE CONNECTION STRING>` with the connection string to the namespace. 4. Replace `<TOPIC NAME>` with the name of the topic. 5. Replace `<SUBSCRIPTION NAME>` with the name of the subscription to the topic. 6. Then run the command in a command prompt to execute this file. ```console node receivefromsubscription.js ``` ### [Connection string](#tab/connection-string) 1. Open your favorite editor, such as [Visual Studio Code](https://code.visualstudio.com/) 2. Create a file called **receivefromsubscription.js** and paste the following code into it. See code comments for details. ```javascript const { delay, ServiceBusClient, ServiceBusMessage } = require("@azure/service-bus"); const connectionString = "<SERVICE BUS NAMESPACE CONNECTION STRING>" const topicName = "<TOPIC NAME>"; const subscriptionName = "<SUBSCRIPTION NAME>"; async function main() { // create a Service Bus client using the connection string to the Service Bus namespace const sbClient = new ServiceBusClient(connectionString); // createReceiver() can also be used to create a receiver for a queue. const receiver = sbClient.createReceiver(topicName, subscriptionName); // function to handle messages const myMessageHandler = async (messageReceived) => { console.log(`Received message: ${messageReceived.body}`); }; // function to handle any errors const myErrorHandler = async (error) => { console.log(error); }; // subscribe and specify the message and error handlers receiver.subscribe({ processMessage: myMessageHandler, processError: myErrorHandler }); // Waiting long enough before closing the sender to send messages await delay(5000); await receiver.close(); await sbClient.close(); } // call the main function main().catch((err) => { console.log("Error occurred: ", err); process.exit(1); }); ``` 3. Replace `<SERVICE BUS NAMESPACE CONNECTION STRING>` with the connection string to the namespace. 4. Replace `<TOPIC NAME>` with the name of the topic. 5. Replace `<SUBSCRIPTION NAME>` with the name of the subscription to the topic. 6. Then run the command in a command prompt to execute this file. ```console node receivefromsubscription.js ``` --- You should see the following output. ```console Received message: Albert Einstein Received message: Werner Heisenberg Received message: Marie Curie Received message: Steven Hawking Received message: Isaac Newton Received message: Niels Bohr Received message: Michael Faraday Received message: Galileo Galilei Received message: Johannes Kepler Received message: Nikolaus Kopernikus ``` In the Azure portal, navigate to your Service Bus namespace, switch to **Topics** in the bottom pane, and select your topic to see the **Service Bus Topic** page for your topic. On this page, you should see 10 incoming and 10 outgoing messages in the **Messages** chart. :::image type="content" source="./media/service-bus-nodejs-how-to-use-topics-subscriptions/topic-page-portal.png" alt-text="Incoming and outgoing messages"::: If you run only the send app next time, on the **Service Bus Topic** page, you see 20 incoming messages (10 new) but 10 outgoing messages. :::image type="content" source="./media/service-bus-nodejs-how-to-use-topics-subscriptions/updated-topic-page.png" alt-text="Updated topic page"::: On this page, if you select a subscription in the bottom pane, you get to the **Service Bus Subscription** page. You can see the active message count, dead-letter message count, and more on this page. In this example, there are 10 active messages that haven't been received by a receiver yet. :::image type="content" source="./media/service-bus-nodejs-how-to-use-topics-subscriptions/active-message-count.png" alt-text="Active message count"::: ## Troubleshooting If you receive an error when running the **passwordless** version of the JavaScript code about required claims, make sure you are signed in via the Azure CLI command, `az login` and the [appropriate role](#azure-built-in-roles-for-azure-service-bus) is applied to your Azure user account. ## Clean up resources Navigate to your Service Bus namespace in the Azure portal, and select **Delete** on the Azure portal to delete the namespace and the queue in it. ## Next steps See the following documentation and samples: - [Azure Service Bus client library for JavaScript](https://www.npmjs.com/package/@azure/service-bus) - [JavaScript samples](/samples/azure/azure-sdk-for-js/service-bus-javascript/) - [TypeScript samples](/samples/azure/azure-sdk-for-js/service-bus-typescript/) - [API reference documentation](/javascript/api/overview/azure/service-bus)