---
title: Quickstart for adding feature flags to JavaScript apps
titleSuffix: Azure App Configuration
description: In this quickstart, add feature flags to a Node.js app and manage them using Azure App Configuration.
author: zhiyuanliang-ms
ms.service: azure-app-configuration
ms.devlang: javascript
ms.topic: quickstart
ms.date: 09/26/2024
ms.author: zhiyuanliang
ms.custom: quickstart, mode-other, devx-track-js
#Customer intent: As a JavaScript developer, I want to use feature flags to control feature availability quickly and confidently.
---

# Quickstart: Add feature flags to a Node.js console app

In this quickstart, you incorporate Azure App Configuration into a Node.js console app to create an end-to-end implementation of feature management. You can use App Configuration to centrally store all your feature flags and control their states.

The JavaScript Feature Management libraries extend the framework with feature flag support. They seamlessly integrate with App Configuration through its JavaScript configuration provider. As an example, this tutorial shows how to use the JavaScript Feature Management in a Node.js app.

## Prerequisites

- An Azure account with an active subscription. [Create one for free](https://azure.microsoft.com/free/).
- An App Configuration store. [Create a store](./quickstart-azure-app-configuration-create.md#create-an-app-configuration-store).
- [LTS versions of Node.js](https://github.com/nodejs/release#release-schedule). For information about installing Node.js either directly on Windows or using the Windows Subsystem for Linux (WSL), see [Get started with Node.js](/windows/dev-environment/javascript/nodejs-overview)

## Add a feature flag

Add a feature flag called *Beta* to the App Configuration store and leave **Label** and **Description** with their default values. For more information about how to add feature flags to a store using the Azure portal or the CLI, go to [Create a feature flag](./manage-feature-flags.md#create-a-feature-flag).

> [!div class="mx-imgBorder"]
> ![Enable feature flag named Beta](media/quickstart-feature-flag-javascript/add-beta-feature-flag.png)


## Use the feature flag

1. Install the Feature Management by using the `npm install` command.

    ``` console
    npm install @microsoft/feature-management
    ```

1. Create a file named *app.js* and add the following code.

    ``` javascript
    const sleepInMs = require("util").promisify(setTimeout);
    const { load } = require("@azure/app-configuration-provider");
    const { FeatureManager, ConfigurationMapFeatureFlagProvider} = require("@microsoft/feature-management")
    const connectionString = process.env.AZURE_APPCONFIG_CONNECTION_STRING;

    async function run() {
        // Connect to Azure App Configuration using connection string
        const settings = await load(connectionString, {
            featureFlagOptions: {
                enabled: true,
                // Note: selectors must be explicitly provided for feature flags.
                selectors: [{
                    keyFilter: "*"
                }],
                refresh: {
                    enabled: true,
                    refreshIntervalInMs: 10_000
                }
            }
        });

        // Create a feature flag provider which uses a map as feature flag source
        const ffProvider = new ConfigurationMapFeatureFlagProvider(settings);
        // Create a feature manager which will evaluate the feature flag
        const fm = new FeatureManager(ffProvider);

        while (true) {
            await settings.refresh(); // Refresh to get the latest feature flag settings
            const isEnabled = await fm.isEnabled("Beta"); // Evaluate the feature flag
            console.log(`Beta is enabled: ${isEnabled}`);
            await sleepInMs(5000);
        }
    }

    run().catch(console.error);
    ```

## Run the application

1. Set an environment variable named **AZURE_APPCONFIG_CONNECTION_STRING**, and set it to the connection string of your App Configuration store. At the command line, run the following command:

    ### [Windows command prompt](#tab/windowscommandprompt)

    To run the app locally using the Windows command prompt, run the following command and replace `<app-configuration-store-connection-string>` with the connection string of your app configuration store:

    ```cmd
    setx AZURE_APPCONFIG_CONNECTION_STRING "<app-configuration-store-connection-string>"
    ```

    ### [PowerShell](#tab/powershell)

    If you use Windows PowerShell, run the following command and replace `<app-configuration-store-connection-string>` with the connection string of your app configuration store:

    ```azurepowershell
    $Env:AZURE_APPCONFIG_CONNECTION_STRING = "<app-configuration-store-connection-string>"
    ```

    ### [macOS](#tab/unix)

    If you use macOS, run the following command and replace `<app-configuration-store-connection-string>` with the connection string of your app configuration store:

    ```console
    export AZURE_APPCONFIG_CONNECTION_STRING='<app-configuration-store-connection-string>'
    ```

    ### [Linux](#tab/linux)

    If you use Linux, run the following command and replace `<app-configuration-store-connection-string>` with the connection string of your app configuration store:

    ```console
    export AZURE_APPCONFIG_CONNECTION_STRING='<app-configuration-store-connection-string>'
    ```

    ---

1. Run the following command to run the app locally:

    ``` console
    node app.js
    ```

1. You will see the following console outputs because the *Beta* feature flag is disabled.

    ``` console
    Beta is enabled: false
    ```

1. Sign in to the [Azure portal](https://portal.azure.com). Select **All resources**, and select the App Configuration store that you created previously. 

1. Select **Feature manager** and locate the *Beta* feature flag. Enable the flag by selecting the checkbox under **Enabled**.

1. Wait for a few seconds and you will see the console outputs change.

    ``` console
    Beta is enabled: true
    ```

## Next steps

For the full feature rundown of the JavaScript.NET feature management library, continue to the following document.

> [!div class="nextstepaction"]
> [JavaScript Feature Management](./feature-management-javascript-reference.md)

While a feature flag allows you to activate or deactivate functionality in your app, you may want to customize a feature flag based on your app's logic. Feature filters allow you to enable a feature flag conditionally. For more information, continue to the following tutorial.

> [!div class="nextstepaction"]
> [Enable conditional features with feature filters](./howto-feature-filters.md)

Azure App Configuration offers built-in feature filters that enable you to activate a feature flag only during a specific period or to a particular targeted audience of your app. For more information, continue to the following tutorial.

> [!div class="nextstepaction"]
> [Enable features on a schedule](./howto-timewindow-filter.md)

> [!div class="nextstepaction"]
> [Roll out features to targeted audiences](./howto-targetingfilter.md)