react-alpha-beta/lib/Cohort.js

Simple declarative A/B testing component for React.

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});

var _stringify = require('babel-runtime/core-js/json/stringify');

var _stringify2 = _interopRequireDefault(_stringify);

exports.isInCohort = isInCohort;

var _constants = require('./constants');

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

/**
 * Given an `experimentParams` object with `id` and `testCohortSize`,
 * it determines whether the user is in the control group or the experimental
 * group.
 * It maintains a global registery of experiments in an object. This consists of
 * a mapping of experiment ids to random numbers, that can be used to determine
 * if the user is in the experimental group or not.
 * @params {string} experimentParams.testId - Experiment id.
 * @params {number} experimentParams.testCohortSize - Number between 0 and 1
 * that indicates the portion of the users that need to be in the experimental
 * group.
 */
function isInCohort(experimentParams) {
  var experimentId = experimentParams.id;

  // Retrieve from storage or create experiment registery
  var alphaBetaMap = void 0;
  try {
    var jsonStr = global.localStorage.getItem(_constants.localStorageKey);
    alphaBetaMap = jsonStr && JSON.parse(jsonStr) || {};
  } catch (err) {
    alphaBetaMap = {};
  }

  // Get and set a random number (<1) in the registery of the experimentId
  if (!(experimentId in alphaBetaMap)) {
    alphaBetaMap[experimentId] = Math.random();
    var _jsonStr = (0, _stringify2.default)(alphaBetaMap);
    global.localStorage.setItem(_constants.localStorageKey, _jsonStr);
  }

  // Return if this user is in the experiment,
  // if they are below the treshold they are in the cohort
  return alphaBetaMap[experimentId] < experimentParams.testCohortSize;
}