title	description	author	ms.topic	ms.date	ms.reviewer	ms.custom
Create your first durable function in Azure using JavaScript	Create and publish an Azure Durable Function in JavaScript using Visual Studio Code.	anthonychu	quickstart	05/07/2020	azfuncdf, antchu	devx-track-js

Create your first durable function in JavaScript

Durable Functions is an extension of Azure Functions that lets you write stateful functions in a serverless environment. The extension manages state, checkpoints, and restarts for you.

In this article, you learn how to use the Visual Studio Code Azure Functions extension to locally create and test a "hello world" durable function. This function will orchestrate and chain together calls to other functions. You then publish the function code to Azure.

Prerequisites

To complete this tutorial:

Install Visual Studio Code.
Install the Azure Functions VS Code extension
Make sure you have the latest version of the Azure Functions Core Tools.
Durable Functions require an Azure storage account. You need an Azure subscription.
Make sure that you have version 10.x or 12.x of Node.js installed.

[!INCLUDE quickstarts-free-trial-note]

Create your local project

In this section, you use Visual Studio Code to create a local Azure Functions project.

In Visual Studio Code, press F1 (or Ctrl/Cmd+Shift+P) to open the command palette. In the command palette, search for and select Azure Functions: Create New Project....
Choose an empty folder location for your project and choose Select.

Following the prompts, provide the following information:

Prompt	Value	Description
Select a language for your function app project	JavaScript	Create a local Node.js Functions project.
Select a version	Azure Functions v3	You only see this option when the Core Tools aren't already installed. In this case, Core Tools are installed the first time you run the app.
Select a template for your project's first function	Skip for now
Select how you would like to open your project	Open in current window	Reopens VS Code in the folder you selected.

Visual Studio Code installs the Azure Functions Core Tools, if needed. It also creates a function app project in a folder. This project contains the host.json and local.settings.json configuration files.

A package.json file is also created in the root folder.

Install the Durable Functions npm package

To work with Durable Functions in a Node.js function app, you use a library called durable-functions.

Use the View menu or Ctrl+Shift+` to open a new terminal in VS Code.
Install the durable-functions npm package by running npm install durable-functions in the root directory of the function app.

Creating your functions

The most basic Durable Functions app contains three functions:

Orchestrator function - describes a workflow that orchestrates other functions.
Activity function - called by the orchestrator function, performs work, and optionally returns a value.
Client function - a regular Azure Function that starts an orchestrator function. This example uses an HTTP triggered function.

Orchestrator function

You use a template to create the durable function code in your project.

In the command palette, search for and select Azure Functions: Create Function....

Following the prompts, provide the following information:

Prompt	Value	Description
Select a template for your function	Durable Functions orchestrator	Create a Durable Functions orchestration
Provide a function name	HelloOrchestrator	Name of your durable function

You've added an orchestrator to coordinate activity functions. Open HelloOrchestrator/index.js to see the orchestrator function. Each call to context.df.callActivity invokes an activity function named Hello.

Next, you'll add the referenced Hello activity function.

Activity function

In the command palette, search for and select Azure Functions: Create Function....
Following the prompts, provide the following information:

Prompt Value Description

Select a template for your function Durable Functions activity Create an activity function

Provide a function name Hello Name of your activity function

You've added the Hello activity function that is invoked by the orchestrator. Open Hello/index.js to see that it's taking a name as input and returning a greeting. An activity function is where you'll perform actions such as making a database call or performing a computation.

Finally, you'll add an HTTP triggered function that starts the orchestration.

Client function (HTTP starter)

In the command palette, search for and select Azure Functions: Create Function....

Following the prompts, provide the following information:

Prompt	Value	Description
Select a template for your function	Durable Functions HTTP starter	Create an HTTP starter function
Provide a function name	DurableFunctionsHttpStart	Name of your activity function
Authorization level	Anonymous	For demo purposes, allow the function to be called without authentication

You've added an HTTP triggered function that starts an orchestration. Open DurableFunctionsHttpStart/index.js to see that it uses client.startNew to start a new orchestration. Then it uses client.createCheckStatusResponse to return an HTTP response containing URLs that can be used to monitor and manage the new orchestration.

You now have a Durable Functions app that can be run locally and deployed to Azure.

Test the function locally

Azure Functions Core Tools lets you run an Azure Functions project on your local development computer. You're prompted to install these tools the first time you start a function from Visual Studio Code.

To test your function, set a breakpoint in the Hello activity function code (Hello/index.js). Press F5 or select Debug: Start Debugging from the command palette to start the function app project. Output from Core Tools is displayed in the Terminal panel.

[!NOTE] Refer to the Durable Functions Diagnostics for more information on debugging.
Durable Functions requires an Azure Storage account to run. When VS Code prompts you to select a storage account, choose Select storage account.

Following the prompts, provide the following information to create a new storage account in Azure.

Prompt	Value	Description
Select subscription	name of your subscription	Select your Azure subscription
Select a storage account	Create a new storage account
Enter the name of the new storage account	unique name	Name of the storage account to create
Select a resource group	unique name	Name of the resource group to create
Select a location	region	Select a region close to you

In the Terminal panel, copy the URL endpoint of your HTTP-triggered function.
Using your browser, or a tool like Postman or cURL, send an HTTP POST request to the URL endpoint. Replace the last segment with the name of the orchestrator function (HelloOrchestrator). The URL should be similar to http://localhost:7071/api/orchestrators/HelloOrchestrator.

The response is the initial result from the HTTP function letting you know the durable orchestration has started successfully. It is not yet the end result of the orchestration. The response includes a few useful URLs. For now, let's query the status of the orchestration.

Copy the URL value for statusQueryGetUri and paste it in the browser's address bar and execute the request. Alternatively you can also continue to use Postman to issue the GET request.

The request will query the orchestration instance for the status. You should get an eventual response, which shows us the instance has completed, and includes the outputs or results of the durable function. It looks like:

{
    "name": "HelloOrchestrator",
    "instanceId": "9a528a9e926f4b46b7d3deaa134b7e8a",
    "runtimeStatus": "Completed",
    "input": null,
    "customStatus": null,
    "output": [
        "Hello Tokyo!",
        "Hello Seattle!",
        "Hello London!"
    ],
    "createdTime": "2020-03-18T21:54:49Z",
    "lastUpdatedTime": "2020-03-18T21:54:54Z"
}

To stop debugging, press Shift + F5 in VS Code.

After you've verified that the function runs correctly on your local computer, it's time to publish the project to Azure.

[!INCLUDE functions-create-function-app-vs-code]

[!INCLUDE functions-publish-project-vscode]

Test your function in Azure

Copy the URL of the HTTP trigger from the Output panel. The URL that calls your HTTP-triggered function should be in this format: http://<functionappname>.azurewebsites.net/api/orchestrators/HelloOrchestrator
Paste this new URL for the HTTP request into your browser's address bar. You should get the same status response as before when using the published app.

Next steps

You have used Visual Studio Code to create and publish a JavaScript durable function app.

[!div class="nextstepaction"] Learn about common durable function patterns

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quickstart-js-vscode.md

quickstart-js-vscode.md

Create your first durable function in JavaScript

Prerequisites

Create your local project

Install the Durable Functions npm package

Creating your functions

Orchestrator function

Activity function

Client function (HTTP starter)

Test the function locally

Test your function in Azure

Next steps

Prompt	Value	Description
Select a template for your function	Durable Functions activity	Create an activity function
Provide a function name	Hello	Name of your activity function

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quickstart-js-vscode.md

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quickstart-js-vscode.md

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Create your first durable function in JavaScript

Prerequisites

Create your local project

Install the Durable Functions npm package

Creating your functions

Orchestrator function

Activity function

Client function (HTTP starter)

Test the function locally

Test your function in Azure

Next steps