@worktango/feature-flags-node

A Node.js-specific feature flag management package for WorkTango applications, built on top of DevCycle and OpenFeature.

Installation

npm install @worktango/feature-flags-node

Usage

import {
  initializeFeatureFlagProvider,
  getBooleanFlagValue,
  getStringFlagValue,
  getOpenFeatureClient,
} from '@worktango/feature-flags-node';

// Initialize with your DevCycle SDK key
await initializeFeatureFlagProvider({
  sdkKey: 'your-devcycle-sdk-key',
  options: {
    disableAutomaticEventLogging: true,
    configPollingIntervalMS: 5 * 1000,
    eventFlushIntervalMS: 1000,
  },
  strictMode: true, // Optional: When enabled, will throw errors if not properly configured
});

// Set user context for feature flag evaluation
// Note: Custom data should be placed under privateCustomData
const userContext = {
  user_id: 'user123',
  email: '[email protected]',
  privateCustomData: {
    companyId: 123,
    isAdmin: true,
  },
};

// Get boolean feature flag value with user context
const isEnabled = await getBooleanFlagValue('my-feature', false, userContext);

// Get string feature flag value with user context
const stringValue = await getStringFlagValue('my-feature', 'default-value', userContext);

Debug

You can also check how the flags are being evaluated by using our EXPERIMENTAL function.

Don't use this in prod code.

// Inside any function, but before the feature flag evaluation.
// The preference is for this to run a single time, so running on the server start,
// after the FeatureFlag provider started is the best place.
____experimental_featureFlagEvaluationHooks();

Example result:

before hook {
  user: DevCycleUser {
    user_id: '[email protected]',
    email: '[email protected]',
    name: undefined,
    language: undefined,
    country: undefined,
    appVersion: undefined,
    appBuild: undefined,
    customData: undefined,
    privateCustomData: undefined
  },
  variableKey: 'example-feature-flag',
  defaultValue: false,
  metadata: {
    project: { id: 'a0s98f09a8sf09a8sf09a8sfas9', key: 'test-project' },
    environment: { id: 'a9sdg79as8d7ga9sd87ga9sd7', key: 'development' }
  }
}
after hook {
  user: DevCycleUser {
    user_id: '[email protected]',
    email: '[email protected]',
    name: undefined,
    language: undefined,
    country: undefined,
    appVersion: undefined,
    appBuild: undefined,
    customData: undefined,
    privateCustomData: undefined
  },
  variableKey: 'example-feature-flag',
  defaultValue: false,
  metadata: {
    project: { id: 'a0s98f09a8sf09a8sf09a8sfas9', key: 'test-project' },
    environment: { id: 'a9sdg79as8d7ga9sd87ga9sd7', key: 'development' }
  }
} DVCVariable {
  key: 'example-feature-flag',
  isDefaulted: false,
  value: true,
  defaultValue: false,
  eval: {
    reason: 'TARGETING_MATCH',
    details: 'All Users',
    target_id: 'fasf098a0s9f8a1kj414'
  },
  type: 'Boolean'
}

API Reference

Types

• FeatureFlagConfig: Interface for feature flag configuration

  interface FeatureFlagConfig {
    sdkKey: string;
    options?: DevCycleOptionsLocalEnabled; // Optional DevCycle configuration
    strictMode?: boolean; // Optional: When enabled (default: false), will throw an error if the Feature Flag Provider/Client is not properly configured.
    // When disabled, will only log a warning if the Provider/Client is not correctly configured.
  }

Functions

• initializeFeatureFlagProvider(config: FeatureFlagConfig): Initialize the feature flag provider with DevCycle
• getBooleanFlagValue(flag: string, defaultValue: boolean, context?: FeatureFlagUser, options?: FlagEvaluationOptions): Get boolean feature flag value
• getStringFlagValue(flag: string, defaultValue: string, context?: FeatureFlagUser, options?: FlagEvaluationOptions): Get string feature flag value
• getOpenFeatureClient(): Get the OpenFeature client for additional flag types (string, number)
• getFeatureFlagProvider(): Get the DevCycle provider instance
• getFeatureFlagClient(): Get the DevCycle client instance
• ____experimental_featureFlagEvaluationHooks: (Not final version, don't use it for prod code) Check how the flags are being evaluated.

Constants

• ANONYMOUS_FEATURE_FLAG_USER: Default anonymous user context