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Quickstart: Create a JavaScript function in Azure from the command line

  • Article

In this article, you use command-line tools to create a JavaScript function that responds to HTTP requests. After testing the code locally, you deploy it to the serverless environment of Azure Functions.

Important

The content of this article changes based on your choice of the Node.js programming model in the selector at the top of the page. The v4 model is currently in preview and is designed to have a more flexible and intuitive experience for JavaScript and TypeScript developers. Learn more about the differences between v3 and v4 in the upgrade guide.

Completion of this quickstart incurs a small cost of a few USD cents or less in your Azure account.

There's also a Visual Studio Code-based version of this article.

Configure your local environment

Before you begin, you must have the following prerequisites:

  • One of the following tools for creating Azure resources:

Prerequisite check

Verify your prerequisites, which depend on whether you're using Azure CLI or Azure PowerShell for creating Azure resources:

  • In a terminal or command window, run func --version to check that the Azure Functions Core Tools are version 4.x.
  • In a terminal or command window, run func --version to check that the Azure Functions Core Tools are version v4.0.5095 or above.

  • Run az --version to check that the Azure CLI version is 2.4 or later.

  • Run az login to sign in to Azure and verify an active subscription.

Create a local function project

In Azure Functions, a function project is a container for one or more individual functions that each responds to a specific trigger. All functions in a project share the same local and hosting configurations. In this section, you create a function project that contains a single function.

  1. Run the func init command, as follows, to create a functions project in a folder named LocalFunctionProj with the specified runtime:

    func init LocalFunctionProj --javascript

  2. Navigate into the project folder:

    cd LocalFunctionProj

    This folder contains various files for the project, including configurations files named local.settings.json and host.json. Because local.settings.json can contain secrets downloaded from Azure, the file is excluded from source control by default in the .gitignore file.

  3. Add a function to your project by using the following command, where the --name argument is the unique name of your function (HttpExample) and the --template argument specifies the function's trigger (HTTP).

    func new --name HttpExample --template "HTTP trigger" --authlevel "anonymous"

    func new creates a subfolder matching the function name that contains a code file appropriate to the project's chosen language and a configuration file named function.json.

You may find the Azure Functions Core Tools reference helpful.

(Optional) Examine the file contents

If desired, you can skip to Run the function locally and examine the file contents later.

index.js

index.js exports a function that's triggered according to the configuration in function.json.

module.exports = async function (context, req) {
    context.log('JavaScript HTTP trigger function processed a request.');

    const name = (req.query.name || (req.body && req.body.name));
    const responseMessage = name
        ? "Hello, " + name + ". This HTTP triggered function executed successfully."
        : "This HTTP triggered function executed successfully. Pass a name in the query string or in the request body for a personalized response.";

    context.res = {
        // status: 200, /* Defaults to 200 */
        body: responseMessage
    };
}

For an HTTP trigger, the function receives request data in the variable req as defined in function.json. The response is defined as res in function.json and can be accessed using context.res. To learn more, see Azure Functions HTTP triggers and bindings.

function.json

function.json is a configuration file that defines the input and output bindings for the function, including the trigger type.

{
    "bindings": [
        {
            "authLevel": "function",
            "type": "httpTrigger",
            "direction": "in",
            "name": "req",
            "methods": [
                "get",
                "post"
            ]
        },
        {
            "type": "http",
            "direction": "out",
            "name": "res"
        }
    ]
}

Each binding requires a direction, a type, and a unique name. The HTTP trigger has an input binding of type httpTrigger and output binding of type http.

  1. Run the func init command, as follows, to create a functions project in a folder named LocalFunctionProj:

    func init LocalFunctionProj --model V4

    You're then prompted to choose a worker runtime and a language - choose Node for the first and JavaScript for the second.

  2. Navigate into the project folder:

    cd LocalFunctionProj

    This folder contains various files for the project, including configurations files named local.settings.json and host.json. Because local.settings.json can contain secrets downloaded from Azure, the file is excluded from source control by default in the .gitignore file.

  3. Add a function to your project by using the following command:

    func new

    Choose the template for "HTTP trigger". You can keep the default name (httpTrigger) or give it a new name (HttpExample). Your function name must be unique, or you're asked to confirm if your intention is to replace an existing function.

    You can find the function you added in the src/functions directory.

  4. Add Azure Storage connection information in local.settings.json.

    {
    "Values": {       
        "AzureWebJobsStorage": "<Azure Storage connection information>",
        "FUNCTIONS_WORKER_RUNTIME": "node",
        "AzureWebJobsFeatureFlags": "EnableWorkerIndexing"
    }
}

  5. (Optional) If you want to learn more about a particular function, say HTTP trigger, you can run the following command:

    func help httptrigger

Run the function locally

  1. Run your function by starting the local Azure Functions runtime host from the LocalFunctionProj folder.

    func start

    Toward the end of the output, the following lines must appear:

    Screenshot of terminal window output when running function locally.

    Note

    If HttpExample doesn't appear as shown above, you likely started the host from outside the root folder of the project. In that case, use Ctrl+C to stop the host, go to the project's root folder, and run the previous command again.

  2. Copy the URL of your HTTP function from this output to a browser and append the query string ?name=<YOUR_NAME>, making the full URL like http://localhost:7071/api/HttpExample?name=Functions. The browser should display a response message that echoes back your query string value. The terminal in which you started your project also shows log output as you make requests.

  3. When you're done, press Ctrl + C and type y to stop the functions host.

Create supporting Azure resources for your function

Before you can deploy your function code to Azure, you need to create three resources:

  • A resource group, which is a logical container for related resources.
  • A Storage account, which is used to maintain state and other information about your functions.
  • A function app, which provides the environment for executing your function code. A function app maps to your local function project and lets you group functions as a logical unit for easier management, deployment, and sharing of resources.

Use the following commands to create these items. Both Azure CLI and PowerShell are supported.

  1. If you haven't done so already, sign in to Azure:

    az login

    The az login command signs you into your Azure account.

  2. Create a resource group named AzureFunctionsQuickstart-rg in your chosen region:

    az group create --name AzureFunctionsQuickstart-rg --location <REGION>

    The az group create command creates a resource group. In the above command, replace <REGION> with a region near you, using an available region code returned from the az account list-locations command.

  3. Create a general-purpose storage account in your resource group and region:

    az storage account create --name <STORAGE_NAME> --location <REGION> --resource-group AzureFunctionsQuickstart-rg --sku Standard_LRS --allow-blob-public-access false

    The az storage account create command creates the storage account.

    In the previous example, replace <STORAGE_NAME> with a name that is appropriate to you and unique in Azure Storage. Names must contain three to 24 characters numbers and lowercase letters only. Standard_LRS specifies a general-purpose account, which is supported by Functions.

Important

The storage account is used to store important app data, sometimes including the application code itself. You should limit access from other apps and users to the storage account.

  1. Create the function app in Azure:

    az functionapp create --resource-group AzureFunctionsQuickstart-rg --consumption-plan-location <REGION> --runtime node --runtime-version 18 --functions-version 4 --name <APP_NAME> --storage-account <STORAGE_NAME>

    The az functionapp create command creates the function app in Azure. It's recommended that you use the latest version of Node.js, which is currently 18. You can specify the version by setting --runtime-version to 18.

    In the previous example, replace <STORAGE_NAME> with the name of the account you used in the previous step, and replace <APP_NAME> with a globally unique name appropriate to you. The <APP_NAME> is also the default DNS domain for the function app.

    This command creates a function app running in your specified language runtime under the Azure Functions Consumption Plan, which is free for the amount of usage you incur here. The command also creates an associated Azure Application Insights instance in the same resource group, with which you can monitor your function app and view logs. For more information, see Monitor Azure Functions. The instance incurs no costs until you activate it.

Update app settings

To enable your V4 programming model app to run in Azure, you need to add a new application setting named AzureWebJobsFeatureFlags with a value of EnableWorkerIndexing. This setting is already in your local.settings.json file.

Run the following command to add this setting to your new function app in Azure. Replace <FUNCTION_APP_NAME> and <RESOURCE_GROUP_NAME> with the name of your function app and resource group, respectively.

az functionapp config appsettings set --name <FUNCTION_APP_NAME> --resource-group <RESOURCE_GROUP_NAME> --settings AzureWebJobsFeatureFlags=EnableWorkerIndexing

Deploy the function project to Azure

After you've successfully created your function app in Azure, you're now ready to deploy your local functions project by using the func azure functionapp publish command.

In the following example, replace <APP_NAME> with the name of your app.

func azure functionapp publish <APP_NAME>

The publish command shows results similar to the following output (truncated for simplicity):

...

Getting site publishing info...
Creating archive for current directory...
Performing remote build for functions project.

...

Deployment successful.
Remote build succeeded!
Syncing triggers...
Functions in msdocs-azurefunctions-qs:
    HttpExample - [httpTrigger]
        Invoke url: https://msdocs-azurefunctions-qs.azurewebsites.net/api/httpexample

Invoke the function on Azure

Because your function uses an HTTP trigger, you invoke it by making an HTTP request to its URL in the browser or with a tool like curl.

Copy the complete Invoke URL shown in the output of the publish command into a browser address bar, appending the query parameter ?name=Functions. The browser should display similar output as when you ran the function locally.

The output of the function run on Azure in a browser

Run the following command to view near real-time streaming logs:

func azure functionapp logstream <APP_NAME>

In a separate terminal window or in the browser, call the remote function again. A verbose log of the function execution in Azure is shown in the terminal.

Clean up resources

If you continue to the next step and add an Azure Storage queue output binding, keep all your resources in place as you'll build on what you've already done.

Otherwise, use the following command to delete the resource group and all its contained resources to avoid incurring further costs.

az group delete --name AzureFunctionsQuickstart-rg

Next steps

Connect to an Azure Storage queue