refactor: Convert lib/core to ES module (Part 1/2) (#449)

Summary:

This converts these folders inside lib/core to ESModule.

lib/core/
  audience_evaluator,
  bucketer, 
  condition_tree_evaluator, 
  custom_attribute_condition_evaluator, 
  decision_service

Test plan:

All unit test and Full stack compatibility suite tests pass.


Co-authored-by: Zeeshan Ashraf <[email protected]>
Co-authored-by: zashraf1985 <[email protected]>

Author: fayyazarshad

packages/optimizely-sdk/lib/core/audience_evaluator/index.js

@@ -1,5 +1,5 @@
 /**
- * Copyright 2016, 2018-2019 Optimizely
+ * Copyright 2016, 2018-2020, Optimizely
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -13,17 +13,19 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-var conditionTreeEvaluator = require('../condition_tree_evaluator');
-var customAttributeConditionEvaluator = require('../custom_attribute_condition_evaluator');
-var enums = require('../../utils/enums');
-var fns = require('../../utils/fns');
-var sprintf = require('@optimizely/js-sdk-utils').sprintf;
-var logging = require('@optimizely/js-sdk-logging');
-var logger = logging.getLogger();
+import { sprintf } from '@optimizely/js-sdk-utils';
+import { getLogger } from '@optimizely/js-sdk-logging';
 
-var ERROR_MESSAGES = enums.ERROR_MESSAGES;
-var LOG_LEVEL = enums.LOG_LEVEL;
-var LOG_MESSAGES = enums.LOG_MESSAGES;
+import fns from '../../utils/fns';
+import {
+  LOG_LEVEL,
+  LOG_MESSAGES, 
+  ERROR_MESSAGES,
+} from '../../utils/enums';
+import conditionTreeEvaluator from '../condition_tree_evaluator';
+import customAttributeConditionEvaluator from '../custom_attribute_condition_evaluator';
+
+var logger = getLogger();
 var MODULE_NAME = 'AUDIENCE_EVALUATOR';
 
 /**
@@ -108,4 +110,4 @@ AudienceEvaluator.prototype.evaluateConditionWithUserAttributes = function(userA
   return null;
 };
 
-module.exports = AudienceEvaluator;
+export default AudienceEvaluator;

packages/optimizely-sdk/lib/core/audience_evaluator/index.tests.js

@@ -1,5 +1,5 @@
 /**
- * Copyright 2016, 2018-2019 Optimizely
+ * Copyright 2016, 2018-2020, Optimizely
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -13,16 +13,15 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-var AudienceEvaluator = require('./');
-var chai = require('chai');
-var conditionTreeEvaluator = require('../condition_tree_evaluator');
-var customAttributeConditionEvaluator = require('../custom_attribute_condition_evaluator');
-var sinon = require('sinon');
-var assert = chai.assert;
-var logging = require('@optimizely/js-sdk-logging');
-var mockLogger = logging.getLogger();
-var enums = require('../../utils/enums');
-var LOG_LEVEL = enums.LOG_LEVEL;
+import sinon from 'sinon';
+import { assert } from 'chai';
+import { getLogger } from '@optimizely/js-sdk-logging';
+
+import AudienceEvaluator from './index';
+import conditionTreeEvaluator from '../condition_tree_evaluator';
+import customAttributeConditionEvaluator from '../custom_attribute_condition_evaluator';
+
+var mockLogger = getLogger();
 
 var chromeUserAudience = {
   conditions: [