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Create a JavaScript function from the command line - Azure Functions
Learn how to create a JavaScript function from the command line, then publish the local Node.js project to serverless hosting in Azure Functions.
11/18/2021
quickstart
javascript
devx-track-azurecli, devx-track-azurepowershell, mode-api

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

[!INCLUDE functions-language-selector-quickstart-cli]

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.

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

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

Configure your local environment

Before you begin, you must have the following:

Prerequisite check

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

Azure CLI

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

  • 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.

Azure PowerShell

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

  • Run (Get-Module -ListAvailable Az).Version and verify version 5.0 or later.

  • Run Connect-AzAccount 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.

(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.

:::code language="javascript" source="~/functions-quickstart-templates/Functions.Templates/Templates/HttpTrigger-JavaScript/index.js":::

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.

:::code language="json" source="~/functions-quickstart-templates/Functions.Templates/Templates/HttpTrigger-JavaScript/function.json":::

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.

[!INCLUDE functions-run-function-test-local-cli]

[!INCLUDE functions-create-azure-resources-cli]

  1. Create the function app in Azure:

    Azure CLI

    az functionapp create --resource-group AzureFunctionsQuickstart-rg --consumption-plan-location <REGION> --runtime node --runtime-version 14 --functions-version 4 --name <APP_NAME> --storage-account <STORAGE_NAME>

    The az functionapp create command creates the function app in Azure. If you're using Node.js 16, also change --runtime-version to 16.

    Azure PowerShell

    New-AzFunctionApp -Name <APP_NAME> -ResourceGroupName AzureFunctionsQuickstart-rg -StorageAccount <STORAGE_NAME> -Runtime node -RuntimeVersion 14 -FunctionsVersion 4 -Location <REGION>

    The New-AzFunctionApp cmdlet creates the function app in Azure. If you're using Node.js 16, change -RuntimeVersion to 16.

    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 provisions 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.

[!INCLUDE functions-publish-project-cli]

[!INCLUDE functions-run-remote-azure-cli]

[!INCLUDE functions-streaming-logs-cli-qs]

[!INCLUDE functions-cleanup-resources-cli]

Next steps

[!div class="nextstepaction"] Connect to an Azure Storage queue