@elliemae/feature-toggle-library

A TypeScript library for managing feature toggles across Encompass Web applications and environments.

EllieMae Encompass Web Feature Toggles

Installation

pnpm add @elliemae/feature-toggle-library

Usage

import {
  isFeatureEnabled,
  FEATURES,
  ENVS,
} from '@elliemae/feature-toggle-library';

// Check if a feature is enabled (uses window.__env.domain automatically)
if (isFeatureEnabled(FEATURES.E_CONSENT)) {
  console.log('E-Consent is enabled');
}

// Check for a specific environment
if (isFeatureEnabled(FEATURES.E_CONSENT, ENVS.QA)) {
  console.log('E-Consent is enabled in QA');
}

// Using string literals (case-insensitive)
if (isFeatureEnabled('e_consent', 'prod')) {
  console.log('E-Consent is enabled in PROD');
}

API

isFeatureEnabled(feature, env?)

Check if a feature is enabled for a given environment.

| Parameter | Type | Description | | --------- | -------- | ----------------------------------------------------------------------------- | | feature | string | Feature name (case-insensitive) | | env | string | Optional. Environment to check. Defaults to window.__env.domain or 'PROD' |

Returns: boolean - true if enabled, false if disabled

FEATURES

Object containing all available feature toggle names as constants.

FEATURES.E_CONSENT; // 'E_CONSENT'
FEATURES.ZZ_TEST_FT_1; // 'ZZ_TEST_FT_1'

ENVS

Object containing all available environment names as constants.

ENVS.PROD; // 'PROD'
ENVS.QA; // 'QA'
ENVS.LOCALHOST; // 'LOCALHOST'

UNDEFINED_FEATURE

Error message thrown when undefined is passed to isFeatureEnabled().

How It Works

1. Source of truth: data/feature-toggles.csv contains all feature toggles and their environment states
2. Build time: pnpm generate converts CSV → JSON (lib/generated/feature-toggles.json)
3. Runtime: isFeatureEnabled() reads the generated JSON to check feature states

The "Negative Storage" Pattern

Features are stored with a "NO means enabled" pattern:

• If METADATA[FEATURE][ENV] is true → feature is DISABLED
• If METADATA[FEATURE][ENV] is false or missing → feature is ENABLED

This matches the legacy @elliemae/encw-feature-toggles behavior.

Development

Setup

pnpm install

Commands

| Command | Description | | --------------- | ---------------------------------------- | | pnpm generate | Generate JSON from CSV | | pnpm test | Run tests (auto-runs generate first) | | pnpm build | Build library (auto-runs generate first) | | pnpm lint | Lint code |

Adding/Updating Feature Toggles

1. Edit data/feature-toggles.xlsx
2. Export to data/feature-toggles.csv
3. Run pnpm test to verify
4. Commit and release

Migration from @elliemae/encw-feature-toggles

This library is a TypeScript rewrite of the legacy @elliemae/encw-feature-toggles package with:

• ✅ Same API (isFeatureEnabled, FEATURES, ENVS)
• ✅ Same behavior (negative storage pattern)
• ✅ TypeScript support with full type definitions
• ✅ Modern build outputs (ESM, CJS, UMD)

Drop-in replacement - just change the import:

- import { isFeatureEnabled, FEATURES } from '@elliemae/encw-feature-toggles';
+ import { isFeatureEnabled, FEATURES } from '@elliemae/feature-toggle-library';

.