adapt to the actual spec draft

packages/core-js/internals/array-group-by.js

@@ -3,24 +3,30 @@ var has = require('../internals/has');
 var IndexedObject = require('../internals/indexed-object');
 var toObject = require('../internals/to-object');
 var toLength = require('../internals/to-length');
-var toPrimitive = require('../internals/to-primitive');
+var toPropertyKey = require('../internals/to-property-key');
 var objectCreate = require('../internals/object-create');
+var arrayFromConstructorAndList = require('../internals/array-from-constructor-and-list');
 
 var push = [].push;
 
-module.exports = function ($this, callbackfn, that, specificCreate) {
+module.exports = function ($this, callbackfn, that, specificConstructor) {
   var O = toObject($this);
   var self = IndexedObject(O);
   var boundFunction = bind(callbackfn, that, 3);
   var target = objectCreate(null);
   var length = toLength(self.length);
   var index = 0;
-  var value, result, array;
+  var Constructor, key, value;
   for (;length > index; index++) {
     value = self[index];
-    result = toPrimitive(boundFunction(value, index, O), 'string');
-    if (has(target, result)) array = target[result];
-    else target[result] = array = specificCreate ? specificCreate($this, 0) : [];
-    push.call(array, value);
+    key = toPropertyKey(boundFunction(value, index, O));
+    if (has(target, key)) push.call(target[key], value);
+    else target[key] = [value];
+  }
+  if (specificConstructor) {
+    Constructor = specificConstructor(O);
+    if (Constructor !== Array) {
+      for (key in target) target[key] = arrayFromConstructorAndList(Constructor, target[key]);
+    }
   } return target;
 };

packages/core-js/modules/esnext.array.group-by.js

@@ -1,14 +1,15 @@
 'use strict';
 var $ = require('../internals/export');
 var $groupBy = require('../internals/array-group-by');
-var arraySpeciesCreate = require('../internals/array-species-create');
+var arraySpeciesConstructor = require('../internals/array-species-constructor');
 var addToUnscopables = require('../internals/add-to-unscopables');
 
 // `Array.prototype.groupBy` method
 // https://github.com/tc39/proposal-array-grouping
 $({ target: 'Array', proto: true }, {
   groupBy: function groupBy(callbackfn /* , thisArg */) {
-    return $groupBy(this, callbackfn, arguments.length > 1 ? arguments[1] : undefined, arraySpeciesCreate);
+    var thisArg = arguments.length > 1 ? arguments[1] : undefined;
+    return $groupBy(this, callbackfn, thisArg, arraySpeciesConstructor);
   }
 });
 

packages/core-js/modules/esnext.typed-array.group-by.js

@@ -1,22 +1,14 @@
 'use strict';
 var ArrayBufferViewCore = require('../internals/array-buffer-view-core');
 var $groupBy = require('../internals/array-group-by');
-var speciesConstructor = require('../internals/species-constructor');
+var typedArraySpeciesConstructor = require('../internals/typed-array-species-constructor');
 
 var aTypedArray = ArrayBufferViewCore.aTypedArray;
-var aTypedArrayConstructor = ArrayBufferViewCore.aTypedArrayConstructor;
 var exportTypedArrayMethod = ArrayBufferViewCore.exportTypedArrayMethod;
 
 // `%TypedArray%.prototype.groupBy` method
 // https://github.com/tc39/proposal-array-grouping
 exportTypedArrayMethod('groupBy', function groupBy(callbackfn /* , thisArg */) {
-  var result = $groupBy(aTypedArray(this), callbackfn, arguments.length > 1 ? arguments[1] : undefined);
-  var TypedArray = aTypedArrayConstructor(speciesConstructor(this, this.constructor));
-  var key, array, typedArray, index, length;
-  for (key in result) {
-    array = result[key];
-    length = array.length;
-    result[key] = typedArray = new TypedArray(length);
-    for (index = 0; index < length; index++) typedArray[index] = array[index];
-  } return result;
+  var thisArg = arguments.length > 1 ? arguments[1] : undefined;
+  return $groupBy(aTypedArray(this), callbackfn, thisArg, typedArraySpeciesConstructor);
 });