Quickstart: Create a JavaScript function in Azure using Visual Studio Code

Use Visual Studio Code to create a JavaScript function that responds to HTTP requests. Test the code locally, then 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's also a CLI-based version of this article.

Configure your environment

Before you get started, make sure you have the following requirements in place:

Create your local project

In this section, you use Visual Studio Code to create a local Azure Functions project in JavaScript. Later in this article, you'll publish your function code to Azure.

  1. Choose the Azure icon in the Activity bar. Then in the Workspace (local) area, select the + button, choose Create Function in the dropdown. When prompted, choose Create new project.

    Screenshot of create a new project window.

  2. Choose the directory location for your project workspace and choose Select. You should either create a new folder or choose an empty folder for the project workspace. Don't choose a project folder that is already part of a workspace.

  3. Provide the following information at the prompts:

    Prompt Selection
    Select a language for your function project Choose JavaScript.
    Select a template for your project's first function Choose HTTP trigger.
    Provide a function name Type HttpExample.
    Authorization level Choose Anonymous, which enables anyone to call your function endpoint. To learn about authorization level, see Authorization keys.
    Select how you would like to open your project Choose Add to workspace.

    Using this information, Visual Studio Code generates an Azure Functions project with an HTTP trigger. You can view the local project files in the Explorer. To learn more about files that are created, see Generated project files.

Run the function locally

Visual Studio Code integrates with Azure Functions Core tools to let you run this project on your local development computer before you publish to Azure.

  1. To start the function locally, press F5 or the Run and Debug icon in the left-hand side Activity bar. The Terminal panel displays the Output from Core Tools. Your app starts in the Terminal panel. You can see the URL endpoint of your HTTP-triggered function running locally.

    Screenshot of the Local function VS Code output.

    If you have trouble running on Windows, make sure that the default terminal for Visual Studio Code isn't set to WSL Bash.

  2. With Core Tools still running in Terminal, choose the Azure icon in the activity bar. In the Workspace area, expand Local Project > Functions. Right-click (Windows) or Ctrl - click (macOS) the new function and choose Execute Function Now....

    Execute function now from Visual Studio Code

  3. In Enter request body you see the request message body value of { "name": "Azure" }. Press Enter to send this request message to your function.

  4. When the function executes locally and returns a response, a notification is raised in Visual Studio Code. Information about the function execution is shown in Terminal panel.

  5. With the Terminal panel focused, press Ctrl + C to stop Core Tools and disconnect the debugger.

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

Sign in to Azure

Before you can publish your app, you must sign in to Azure.

  1. If you aren't already signed in, choose the Azure icon in the Activity bar. Then in the Resources area, choose Sign in to Azure....

    Screenshot of the sign-in to Azure window within VS Code.

    If you're already signed in and can see your existing subscriptions, go to the next section. If you don't yet have an Azure account, choose Create and Azure Account.... Students can choose Create and Azure for Students Account....

  2. When prompted in the browser, choose your Azure account and sign in using your Azure account credentials. If you create a new account, you can sign in after your account is created.

  3. After you've successfully signed in, you can close the new browser window. The subscriptions that belong to your Azure account are displayed in the sidebar.

Create the function app in Azure

In this section, you create a function app and related resources in your Azure subscription.

  1. Choose the Azure icon in the Activity bar. Then in the Resources area, select the + icon and choose the Create Function App in Azure option.

    Create a resource in your Azure subscription

  2. Provide the following information at the prompts:

    Prompt Selection
    Select subscription Choose the subscription to use. You won't see this prompt when you have only one subscription visible under Resources.
    Enter a globally unique name for the function app Type a name that is valid in a URL path. The name you type is validated to make sure that it's unique in Azure Functions.
    Select a runtime stack Choose the language version on which you've been running locally.
    Select a location for new resources For better performance, choose a region near you.

    The extension shows the status of individual resources as they're being created in Azure in the Azure: Activity Log panel.

    Log of Azure resource creation

  3. When the creation is complete, the following Azure resources are created in your subscription. The resources are named based on your function app name:

    • A resource group, which is a logical container for related resources.
    • A standard Azure Storage account, which maintains state and other information about your projects.
    • A function app, which provides the environment for executing your function code. A function app lets you group functions as a logical unit for easier management, deployment, and sharing of resources within the same hosting plan.
    • An App Service plan, which defines the underlying host for your function app.
    • An Application Insights instance connected to the function app, which tracks usage of your functions in the app.

    A notification is displayed after your function app is created and the deployment package is applied.

    Tip

    By default, the Azure resources required by your function app are created based on the function app name you provide. By default, they're also created in the same new resource group with the function app. If you want to either customize the names of these resources or reuse existing resources, you need to publish the project with advanced create options instead.

Deploy the project to Azure

Important

Deploying to an existing function app always overwrites the contents of that app in Azure.

  1. Choose the Azure icon in the Activity bar, then in the Workspace area, select your project folder and select the Deploy... button.

    Deploy project from the Visual Studio Code workspace

  2. Select Deploy to Function App..., choose the function app you just created, and select Deploy.

  3. After deployment completes, select View Output to view the creation and deployment results, including the Azure resources that you created. If you miss the notification, select the bell icon in the lower right corner to see it again.

    Screenshot of the View Output window.

Run the function in Azure

  1. Back in the Resources area in the side bar, expand your subscription, your new function app, and Functions. Right-click (Windows) or Ctrl - click (macOS) the HttpExample function and choose Execute Function Now....

    Screenshot of executing function in Azure from Visual Studio Code.

  2. In Enter request body you see the request message body value of { "name": "Azure" }. Press Enter to send this request message to your function.

  3. When the function executes in Azure and returns a response, a notification is raised in Visual Studio Code.

Change the code and redeploy to Azure

  1. In Visual Studio Code in the Explorer view, select the ./HttpExample/index.js file.

  2. Replace the file with the following code to construct a JSON object and return it.

    module.exports = async function (context, req) {
    
        try {
            context.log('JavaScript HTTP trigger function processed a request.');
    
            // Read incoming data
            const name = (req.query.name || (req.body && req.body.name));
            const sport = (req.query.sport || (req.body && req.body.sport));
    
            // fail if incoming data is required
            if (!name || !sport) {
    
                context.res = {
                    status: 400
                };
                return;
            }
    
            // Add or change code here
            const message = `${name} likes ${sport}`;
    
            // Construct response
            const responseJSON = {
                "name": name,
                "sport": sport,
                "message": message,
                "success": true
            }
    
            context.res = {
                // status: 200, /* Defaults to 200 */
                body: responseJSON,
                contentType: 'application/json'
            };
        } catch(err) {
            context.res = {
                status: 500
            };
        }
    }
    
  3. Rerun the function app locally.

  4. In the prompt Enter request body change the request message body to { "name": "Tom","sport":"basketball" }. Press Enter to send this request message to your function.

  5. View the response in the notification:

    {
      "name": "Tom",
      "sport": "basketball",
      "message": "Tom likes basketball",
      "success": true
    }
    
  6. Redeploy the function to Azure.

Troubleshooting

Use the table below to resolve the most common issues encountered when using this quickstart.

Problem Solution
Can't create a local function project? Make sure you have the Azure Functions extension installed.
Can't run the function locally? Make sure you have the Azure Functions Core Tools installed installed.
When running on Windows, make sure that the default terminal shell for Visual Studio Code isn't set to WSL Bash.
Can't deploy function to Azure? Review the Output for error information. The bell icon in the lower right corner is another way to view the output. Did you publish to an existing function app? That action overwrites the content of that app in Azure.
Couldn't run the cloud-based Function app? Remember to use the query string to send in parameters.

Clean up resources

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

Otherwise, you can use the following steps to delete the function app and its related resources to avoid incurring any further costs.

  1. In Visual Studio Code, select the Azure icon to open the Azure explorer.
  2. In the Resource Groups section, find your resource group.
  3. Right-click the resource group and select Delete.

To learn more about Functions costs, see Estimating Consumption plan costs.

Next steps

You have used Visual Studio Code to create a function app with a simple HTTP-triggered function. In the next article, you expand that function by connecting to either Azure Cosmos DB or Azure Storage. To learn more about connecting to other Azure services, see Add bindings to an existing function in Azure Functions. If you want to learn more about security, see Securing Azure Functions.