a.js

import * as optimizelySDK from "@optimizely/js-web-sdk";
import OptimizelySingleton from "./index";

describe("OptimizelySingleton", () => {
  const localIsFeatureEnabled = jest.fn();

  beforeEach(() => {
    optimizelySDK.createInstance = jest.fn(() => ({
      isFeatureEnabled: (featureName, userId) => localIsFeatureEnabled(featureName, userId),
    }));
  });

  describe("when the member's ID is provided", () => {
    it("invokes Optimizely with the member's ID", () => {
      OptimizelySingleton.isFeatureEnabled("FEATURE_SPAM", 42);
      expect(localIsFeatureEnabled).toHaveBeenCalledWith("FEATURE_SPAM", "MEMBER:42");
    });
  });

  describe("when the member's ID is NOT provided", () => {
    it("invokes Optimizely with the member's ID", () => {
      OptimizelySingleton.isFeatureEnabled("FEATURE_EGGS", undefined);
      expect(localIsFeatureEnabled).toHaveBeenCalledWith("FEATURE_EGGS", "MEMBER:ANONYMOUS");
    });
  });
});

b.js

import OptimizelySingleton from "./optimizely/index";

export function loginToTheFrontEnabled() {
  return typeof FEATURE_LOGIN_TO_THE_FRONT !== "undefined" && FEATURE_LOGIN_TO_THE_FRONT === "ON";
}

export function standAloneLoginEnabled() {
  return typeof FEATURE_STAND_ALONE_LOGIN !== "undefined" && FEATURE_STAND_ALONE_LOGIN === "ON";
}

export function v2SaveAndCloseProperty() {
  return (
    typeof FEATURE_V2_SAVE_AND_CLOSE_PROPERTY !== "undefined" &&
    FEATURE_V2_SAVE_AND_CLOSE_PROPERTY === "ON"
  );
}

export function v2SaveAndClosePerson() {
  return (
    typeof FEATURE_V2_SAVE_AND_CLOSE_PERSON !== "undefined" &&
    FEATURE_V2_SAVE_AND_CLOSE_PERSON === "ON"
  );
}

export function inspectionsEnabled() {
  return typeof FEATURE_INSPECTIONS !== "undefined" && FEATURE_INSPECTIONS === "ON";
}

export function freeAreaBannerEnabled() {
  return typeof FEATURE_INSPECTIONS !== "undefined" && FEATURE_TOWNSVILLE_FLOODS_BANNER === "ON";
}

export function breadcrumbsEnabled() {
  return typeof FEATURE_BREADCRUMBS !== "undefined" && FEATURE_BREADCRUMBS === "ON";
}

export function paginationEnabled() {
  return typeof FEATURE_PAGINATION !== "undefined" && FEATURE_PAGINATION === "ON";
}

export function propertyBoostEnabled() {
  return typeof FEATURE_PROPERTY_BOOST !== "undefined" && FEATURE_PROPERTY_BOOST === "ON";
}

export function roomFeaturesEnabled() {
  return typeof FEATURE_ROOM_FEATURES !== "undefined" && FEATURE_ROOM_FEATURES === "ON";
}

export const enquireByRoomEnabled = memberId =>
  OptimizelySingleton.isFeatureEnabled("FEATURE_ENQUIRE_BY_ROOM", memberId);

export function focusInspectionsEnabled() {
  return typeof FEATURE_FOCUS_INSPECTIONS !== "undefined" && FEATURE_FOCUS_INSPECTIONS === "ON";
}

c.js

import * as optimizelySDK from "@optimizely/js-web-sdk";

const OptimizelySingleton = (function() {
  let instance;
  let featuresCache = {};

  const createInstance = () => {
    const optimizelyClient = optimizelySDK.createInstance({
      sdkKey: process.env.OPTIMIZELY_KEY,
      logLevel: 4,
    });
    return optimizelyClient;
  };

  return {
    getInstance: () => {
      if (!instance) {
        instance = createInstance();
      }
      return instance;
    },
    isFeatureEnabled: (featureName, userId) => {
      const memberId = userId ? `MEMBER:${userId}` : "MEMBER:ANONYMOUS";
      if (!featuresCache[featureName]) {
        featuresCache[featureName] = OptimizelySingleton.getInstance().isFeatureEnabled(
          featureName,
          memberId
        );
      }
      return featuresCache[featureName];
    },
  };
})();

export default OptimizelySingleton;