VWO Feature Management and Experimentation SDK for React SDK

Overview

The VWO Feature Management and Experimentation SDK (VWO FME React SDK) enables React.js developers to integrate feature flagging and experimentation into their applications. This SDK provides full control over feature rollout, A/B testing, and event tracking, allowing teams to manage features dynamically and gain insights into user behavior.

Requirements

• React 16.8+

Installation

Install the SDK via npm or yarn:

# via npm
npm install vwo-fme-react-sdk --save

# via yarn
yarn add vwo-fme-react-sdk

Getting Started with VWOProvider

Basic Implementation

import React from 'react';
import { VWOProvider, IVWOOptions, IVWOContextModel } from 'vwo-fme-react-sdk';

const vwoConfig: IVWOOptions = {
  sdkKey: '32-alpha-numeric-sdk-key', // Your VWO SDK Key
  accountId: '123456', // Your VWO Account ID
  logger: {
    level: 'debug', // Optional log level for debugging
  },
};

const userContext: IVWOContextModel = {
  id: 'unique_user_id', // Required: Unique identifier for the user
  customVariables: { age: 25, location: 'US' }, // Optional
  userAgent:
    'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36', // Optional
  ipAddress: '1.1.1.1', // Optional
};

// Optional: Provide a fallback UI component that will be displayed while VWOProvider initializes.
// This is useful for showing a loading state or placeholder content during SDK initialization.
const fallbackComponent = <div>Initializing VWO...</div>;

const App = () => (
  <VWOProvider config={vwoConfig} userContext={userContext} fallbackComponent={fallbackComponent}>
    <YourComponent />
  </VWOProvider>
);

export default App;

Using Pre-initialized VWO Client

If you have already initialized a VWO client in your application, you can pass it directly to the VWOProvider:

import React, { useEffect, useState } from 'react';
import { VWOProvider, IVWOOptions, IVWOClient, IVWOContextModel, init } from 'vwo-fme-react-sdk';

const vwoConfig: IVWOOptions = {
  sdkKey: '32-alpha-numeric-sdk-key', // Replace with your real SDK key
  accountId: '123456', // Replace with your real account ID
  logger: {
    level: 'debug',
  },
};

const userContext: IVWOContextModel = {
  id: 'unique_user_id',
  customVariables: { age: 25, location: 'US' },
  userAgent: 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36',
  ipAddress: '1.1.1.1',
};

const fallbackComponent = <div>Initializing VWO...</div>;

const App = () => {
  const [vwoClient, setVwoClient] = useState<IVWOClient | null>(null);

  useEffect(() => {
    const initializeVWO = async () => {
      const client = await init(vwoConfig);
      setVwoClient(client);
    };

    initializeVWO();
  }, []);

  if (!vwoClient) return fallbackComponent;

  return (
    <VWOProvider client={vwoClient} userContext={userContext}>
      <YourComponent />
    </VWOProvider>
  );
};

export default App;

Basic Implementation without User Context

If you don't have user details available while initialising the VWOProvider you can pass it later in useGetFlag hook.

import React from 'react';
import { VWOProvider, IVWOOptions, IVWOContextModel } from 'vwo-fme-react-sdk';

const vwoConfig: IVWOOptions = {
  sdkKey: '32-alpha-numeric-sdk-key', // Your VWO SDK Key
  accountId: '123456', // Your VWO Account ID
  logger: {
    level: 'debug', // Optional log level for debugging
  },
};

// Optional: Provide a fallback UI component that will be displayed while VWOProvider initializes.
// This is useful for showing a loading state or placeholder content during SDK initialization.
const fallbackComponent = <div>Initializing VWO...</div>;

const App = () => (
  <VWOProvider config={vwoConfig} fallbackComponent={fallbackComponent}>
    <YourComponent />
  </VWOProvider>
);

export default App;

To learn more about on how to pass context in useGetFlag hook, click here.

Advanced Configuration Options

To customize the SDK further, additional parameters can be passed to the VWOProvider component using config parameter. Here’s a table describing each option:

Parameter	Description	Required	Type	Example
accountId	VWO Account ID for authentication.	Yes	String	'123456'
sdkKey	SDK key corresponding to the specific environment to initialize the VWO SDK Client. You can get this key from VWO Application.	Yes	String	'32-alpha-numeric-sdk-key'
pollInterval	Time interval for fetching updates from VWO servers (in milliseconds).	No	Number	60000
storage	Custom storage connector for persisting user decisions and campaign data.	No	Object	See Storage section
logger	Toggle log levels for more insights or for debugging purposes. You can also customize your own transport in order to have better control over log messages.	No	Object	See Logger section

Refer to the official VWO documentation for additional parameter details.

Available Hooks

The VWO FME React SDK offers a comprehensive suite of React hooks that enable seamless integration of feature management and experimentation capabilities into your application. Here are the key hooks available:

Hook	Definition	Example
useGetFlag	Retrieve feature flag status and variables for a specific user	Learn how to use feature flags
useGetFlagVariable	Access individual feature flag variables	Learn how to access individual variables
useGetFlagVariables	Get all variables associated with a feature flag	Learn how to access all flag variables
useTrackEvent	Track custom events and user interactions	Learn how to track user events
useSetAttribute	Set user attributes for targeting and segmentation	Learn how to set user attributes
useVWOClient	Access the underlying VWO client instance	Learn how to access VWO client

User Context

The context object uniquely identifies users and is crucial for consistent feature rollouts. A typical context includes an id for identifying the user. It can also include other attributes that can be used for targeting and segmentation, such as customVariables, userAgent and ipAddress.

Parameters Table

The following table explains all the parameters in the context object:

Parameter	Description	Required	Type	Example
id	Unique identifier for the user.	Yes	String	'unique_user_id'
customVariables	Custom attributes for targeting.	No	Object	{ age: 25, location: 'US' }
userAgent	User agent string for identifying the user's browser and operating system.	No	String	'Mozilla/5.0 ... Safari/537.36'
ipAddress	IP address of the user.	No	String	'1.1.1.1'

Example

import { IVWOContextModel } from 'vwo-fme-react-sdk';

const userContext: IVWOContextModel = {
  id: 'unique_user_id',
  customVariables: { age: 25, location: 'US' },
  userAgent:
    'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36',
  ipAddress: '1.1.1.1',
};

VWO Client Usage

The useVWOClient hook provides direct access to the underlying VWO client instance, allowing you to utilize all available VWO client methods like getFlag, trackEvent and setAttribute.

Hook Return Type

Property	Description	Type
vwoClient	VWO client instance with access to all client methods	IVWOClient
isReady	Boolean indicating whether the VWO SDK client has initialized successfully	boolean

Example Usage

import React, { useEffect, useState } from 'react';
import { useVWOClient, IVWOContextModel } from 'vwo-fme-react-sdk';

const FeatureFlagComponent = () => {
  const [isFeatureEnabled, setIsFeatureEnabled] = useState(false);
  const {vwoClient, isReady } = useVWOClient();

  useEffect(() => {
    const checkFeature = async () => {
      if (!isReady) {
        console.log('VWO Client not available');
        return;
      }

      // Define user context (could be dynamic)
      const userContext: IVWOContextModel = { id: 'unique_user_id' };

      try {
        // Fetch the feature flag using getFlag method
        const flag = await vwoClient.getFlag('feature_key', userContext);

        // Check if the feature is enabled
        setIsFeatureEnabled(flag.isEnabled());
      } catch (error) {
        console.error('Error checking feature flag:', error);
      }
    };

    checkFeature();
  }, [vwoClient, isReady]);

  return (
    <div>
      {isFeatureEnabled ? (
        <p>The feature is enabled!</p>
      ) : (
        <p>The feature is not enabled.</p>
      )}
    </div>
  );
};

export default FeatureFlagComponent;

Basic Feature Flagging

Feature Flags serve as the foundation for all testing, personalization, and rollout rules within FME. To implement a feature flag, first use the useGetFlag hook to retrieve the flag configuration. The useGetFlag hook provides a simple way to check if a feature is enabled for a specific user and access its variables. It returns a feature flag object that contains methods for checking the feature's status and retrieving any associated variables.

Hook Parameters

Parameter	Description	Required	Type	Example
featureKey	Unique identifier of the feature flag	Yes	String	'new_checkout'
context	User Context to be passed, if not at the time of VWOProvider	No	Object	{ id: 'unique_user_id'}

Hook Return Type

The useGetFlag hook returns a flag object and an isReady boolean that indicates when the VWO SDK client has initialized and the flag data is available.

Property	Description	Type
flag	Feature flag object containing status and variables	IFlag
isReady	Boolean indicating whether the VWO SDK client has initialized successfully	boolean

The IFlag object contains methods and properties for checking feature status and accessing variables. It is recommended to check isReady before using the flag object to ensure proper initialization.

Use the isReady flag to determine when the feature flag data has been fully initialized and is safe to access. This helps prevent rendering based on incomplete or default flag values, thereby avoiding flicker or inconsistent UI states.

Example Usage if userContext was already provided in VWOProvider.

import React from 'react';
import { useGetFlag, useGetFlagVariable, useGetFlagVariables } from 'vwo-fme-react-sdk'; // Import hooks

const YourComponent = () => {
  // Retrieve the flag using the feature key
  const { flag, isReady } = useGetFlag('feature_key');

  // Or, pass userContext, if not provided at the time of using VWOProvider or you want to use updated user context
  // const { flag, isReady } = useGetFlag('feature_key', userContext);

  if (!isReady) { return <div>Default/Zero state</div>; }

  // Use the flag object returned by useGetFlag to retrieve a specific variable
  const variableValue = useGetFlagVariable(flag, "variable-value", "default-value");
  const allVariable = useGetFlagVariable(flag);

  return (
    <div>
      {/* Display the feature flag variable value */}
      <p>Feature Flag Variable Value: {variableValue}</p>
    </div>
  );
};

export default YourComponent;

Example Usage if userContext was not provided in VWOProvider.

import React from 'react';
import { useGetFlag, useGetFlagVariable, IVWOContextModel } from 'vwo-fme-react-sdk'; // Import hooks

const YourComponent = () => {

  const userContext: IVWOContextModel = {
    id: 'unique_user_id',
    customVariables: { age: 25, location: 'US' },
    userAgent: 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36',
    ipAddress: '1.1.1.1',
  };
  // Retrieve the flag using the feature key
  const { flag, isReady } = useGetFlag('feature_key', userContext);

  if (!isReady) { return <div>Default/Zero state</div>; }

  // Use the flag object returned by useGetFlag to retrieve a specific variable
  const variableValue = useGetFlagVariable(flag, "variable-value", "default-value");

  return (
    <div>
      {/* Display the feature flag variable value */}
      <p>Feature Flag Variable Value: {variableValue}</p>
    </div>
  );
};

export default YourComponent;

Custom Event Tracking

Feature flags can be enhanced with connected metrics to track key performance indicators (KPIs) for your features. These metrics help measure the effectiveness of your testing rules by comparing control versus variation performance, and evaluate the impact of personalization and rollout campaigns. Use the useTrackEvent hook to track custom events like conversions, user interactions, and other important metrics.

The useTrackEvent hook returns an object containing a trackEvent function and an isReady boolean. The trackEvent function allows you to track custom events and conversions, while isReady indicates if the hook is ready to be used. The trackEvent function accepts the following parameters:

Parameter	Description	Required	Type	Example
eventName	Name of the event you want to track	Yes	String	'purchase_completed'
eventProperties	Additional properties/metadata associated with the event	No	Object	{ amount: 49.99 }

Example usage:

import { useTrackEvent } from 'vwo-fme-react-sdk';

function YourComponent() {
  const { trackEvent, isReady } = useTrackEvent();

  return <button onClick={() => trackEvent('button_clicked')}>Click Me</button>;
}

See Tracking Conversions documentation for more information.

Pushing Attributes

User attributes provide rich contextual information about users, enabling powerful personalization. The useSetAttribute hook provides a simple way to associate these attributes with users in VWO for advanced segmentation. The useSetAttribute hook returns an object containing a setAttribute function and an isReady boolean. The setAttribute allows you to set user attribute, while isReady indicates if the hook is ready to be used. This setAttribute function accepts the following parameters:

Parameter	Description	Required	Type	Example
attributeMap	A key-value map of attributes to set for the user. The keys are attribute names and values are the corresponding attribute values.	Yes	Object	{ age: 25, location: 'US' }

Example usage:

import { useSetAttribute } from 'vwo-fme-react-sdk';

function YourComponent() {
  const { setAttribute, isReady } = useSetAttribute();

  return <button onClick={() => setAttribute({ age: 25, location: 'US' })}>Click Me</button>;
}

See Pushing Attributes documentation for additional information.

Polling Interval Adjustment

The pollInterval is an optional parameter that allows the SDK to automatically fetch and update settings from the VWO server at specified intervals. Setting this parameter ensures your application always uses the latest configuration.

import { VWOProvider, IVWOOptions, IVWOContextModel } from 'vwo-fme-react-sdk';
const vwoConfig: IVWOOptions = {
  sdkKey: '32-alpha-numeric-sdk-key', // Your VWO SDK Key
  accountId: '123456', // Your VWO Account ID
  pollInterval: 60000, // Time interval for fetching updates from VWO servers (in milliseconds)
};

const userContext: IVWOContextModel = { id: 'unique_user_id' };

const App = () => (
  <VWOProvider config={vwoConfig} userContext={userContext}>
    <YourComponent />
  </VWOProvider>
);

Storage

The SDK operates in a stateless mode by default, meaning each useGetFlag hook triggers a fresh evaluation of the flag against the current user context.

To optimize performance and maintain consistency, you can implement a custom storage mechanism by passing a storage parameter during initialization. This allows you to persist feature flag decisions in your preferred database system (like Redis, MongoDB, or any other data store).

Key benefits of implementing storage:

• Improved performance by caching decisions
• Consistent user experience across sessions
• Reduced load on your application

The storage mechanism ensures that once a decision is made for a user, it remains consistent even if campaign settings are modified in the VWO Application. This is particularly useful for maintaining a stable user experience during A/B tests and feature rollouts.

import { VWOProvider, IVWOOptions, IVWOContextModel, StorageConnector } from 'vwo-fme-react-sdk';

class StorageConnector extends StorageConnector {
  constructor() {
    super();
  }

  /**
   * Get data from storage
   * @param {string} featureKey
   * @param {string} userId
   * @returns {Promise<any>}
   */
  async get(featureKey, userId) {
    // return await data (based on featureKey and userId)
  }

  /**
   * Set data in storage
   * @param {object} data
   */
  async set(data) {
    // Set data corresponding to a featureKey and user ID
    // Use data.featureKey and data.userId to store the above data for a specific feature and a user
  }
}

const vwoConfig: IVWOOptions = {
  sdkKey: '32-alpha-numeric-sdk-key', // Your VWO SDK Key
  accountId: '123456', // Your VWO Account ID
  logger: {
    level: 'debug', // Optional log level for debugging
  },
  storage: StorageConnector,
};

const userContext: IVWOContextModel = {id: 'unique_user_id'};

const App = () => (
  <VWOProvider config={vwoConfig} userContext={userContext}>
    <YourComponent />
  </VWOProvider>
);

export default App;

Logger

VWO by default logs all ERROR level messages to your server console. To gain more control over VWO's logging behaviour, you can use the logger parameter in the init configuration.

Parameter	Description	Required	Type	Example
level	Log level to control verbosity of logs	Yes	String	DEBUG
prefix	Custom prefix for log messages	No	String	'CUSTOM LOG PREFIX'

Example 1: Set log level to control verbosity of logs

import { VWOProvider, IVWOOptions, IVWOContextModel } from 'vwo-fme-react-sdk';
const vwoConfig: IVWOOptions = {
  sdkKey: '32-alpha-numeric-sdk-key', // SDK Key
  accountId: '123456', // VWO Account ID
  logger: {
    level: 'debug',
  },
};

const userContext: IVWOContextModel = {id: 'unique_user_id'};

const App = () => (
  <VWOProvider config={vwoConfig} userContext={userContext}>
    <YourComponent />
  </VWOProvider>
);

export default App;

Example 2: Add custom prefix to log messages for easier identification

import { VWOProvider, IVWOOptions, IVWOContextModel } from 'vwo-fme-react-sdk';
const vwoConfig: IVWOOptions = {
  sdkKey: '32-alpha-numeric-sdk-key', // SDK Key
  accountId: '123456', // VWO Account ID
  logger: {
    level: 'debug',
    prefix: 'CUSTOM LOG PREFIX', // custom logger prefix
  },
};

const userContext: IVWOContextModel = {id: 'unique_user_id'};

const App = () => (
  <VWOProvider config={vwoConfig} userContext={userContext}>
    <YourComponent />
  </VWOProvider>
);

export default App;

Version History

The version history tracks changes, improvements, and bug fixes in each version. For a full history, see the CHANGELOG.md.

Development and Testing

Install Dependencies and Bootstrap Git Hooks

yarn install

Compile TypeScript to JavaScript

yarn build

Contributing

We welcome contributions to improve this SDK! Please read our contributing guidelines before submitting a PR.

Code of Conduct

Our Code of Conduct outlines expectations for all contributors and maintainers.

License

Apache License, Version 2.0

Copyright 2025 Wingify Software Pvt. Ltd.