diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4a750ca2ee74..6e03515a43eb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,11 @@
     - `String.prototype.toWellFormed` method
   - Moved to stable ES, [May 2023 TC39 meeting](https://github.com/tc39/proposal-is-usv-string/pull/31)
   - Added `es.` namespace modules, `/es/` and `/stable/` namespaces entries
+- [`Array` grouping proposal](https://github.com/tc39/proposal-array-grouping):
+  - Because of the [web compat issue](https://github.com/tc39/proposal-array-grouping/issues/44), [moved from prototype to static methods](https://github.com/tc39/proposal-array-grouping/pull/47), [May 2023 TC39 meeting](https://github.com/babel/proposals/issues/88#issuecomment-1553350818). Added:
+    - `Object.groupBy`
+    - `Map.groupBy`
+  - Demoted to stage 2
 - [Decorator Metadata proposal](https://github.com/tc39/proposal-decorator-metadata):
   - Moved to Stage 3, [May 2023 TC39 meeting](https://github.com/babel/proposals/issues/88#issuecomment-1553366034)
   - Added `Function.prototype[Symbol.metadata]` (`=== null`), [May 2023 TC39 meeting](https://github.com/babel/proposals/issues/88#issuecomment-1550313363)
@@ -23,7 +28,7 @@
 - Fixed awaiting async `AsyncDisposableStack.prototype.adopt` callback, [#1258](https://github.com/zloirock/core-js/issues/1258)
 - Compat data improvements:
   - `Set.prototype.difference` that was missed in Bun because of [a bug](https://github.com/oven-sh/bun/issues/2309) added in 0.6.0
-  - `Array.prototype.{ group, groupToMap }` are disabled from Bun 0.6.2 because of [web compat issues](https://github.com/tc39/proposal-array-grouping/issues/44)
+  - `Array.prototype.{ group, groupToMap }` marked as no longer supported in WebKit runtimes because of the mentioned above web compat issue. For example, it's disabled from Bun 0.6.2
   - Added Deno 1.34 compat data mapping
   - Added Electron 26 compat data mapping
   - Added Samsung Internet 22 compat data mapping
diff --git a/README.md b/README.md
index f40ad4118489..196b0f60ca2b 100644
--- a/README.md
+++ b/README.md
@@ -2238,28 +2238,6 @@ core-js(-pure)/full/array/from-async
 ```js
 await Array.fromAsync((async function * (){ yield * [1, 2, 3] })(), i => i * i); // => [1, 4, 9]
 ```
-##### [`Array` grouping](https://github.com/tc39/proposal-array-grouping)[⬆](#index)
-Modules [`esnext.array.group`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.array.group.js), [`esnext.array.group-to-map`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.array.group-to-map.js).
-```js
-class Array {
-  group(callbackfn: (value: any, index: number, target: any) => key, thisArg?: any): { [key]: Array<mixed> };
-  groupToMap(callbackfn: (value: any, index: number, target: any) => key, thisArg?: any): Map<key, Array<mixed>>;
-}
-```
-[*CommonJS entry points:*](#commonjs-api)
-```
-core-js/proposals/array-grouping-stage-3-2
-core-js(-pure)/actual|full/array(/virtual)/group
-core-js(-pure)/actual|full/array(/virtual)/group-to-map
-```
-[*Examples*](https://is.gd/3a0PbH):
-```js
-[1, 2, 3, 4, 5].group(it => it % 2); // => { 1: [1, 3, 5], 0: [2, 4] }
-
-const map = [1, 2, 3, 4, 5].groupToMap(it => it % 2);
-map.get(1); // => [1, 3, 5]
-map.get(0); // => [2, 4]
-````
 ##### [New `Set` methods](https://github.com/tc39/proposal-set-methods)[⬆](#index)
 Modules [`esnext.set.difference.v2`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.set.difference.v2.js), [`esnext.set.intersection.v2`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.set.intersection.v2.js), [`esnext.set.is-disjoint-from.v2`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.set.is-disjoint-from.v2.js), [`esnext.set.is-subset-of.v2`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.set.is-subset-of.v2.js), [`esnext.set.is-superset-of.v2`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.set.is-superset-of.v2.js), [`esnext.set.symmetric-difference.v2`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.set.symmetric-difference.v2.js), [`esnext.set.union.v2`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.set.union.v2.js)
 ```js
@@ -2425,6 +2403,31 @@ core-js(-pure)/actual|full/function/metadata
 ```
 core-js(-pure)/stage/2
 ```
+##### [`Array` grouping](https://github.com/tc39/proposal-array-grouping)[⬆](#index)
+Modules [`esnext.object.group-by`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.object.group-by.js), [`esnext.map.group-by`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.map.group-by.js).
+```js
+class Object {
+  groupBy(items: Iterable, callbackfn: (value: any, index: number) => key): { [key]: Array<mixed> };
+}
+
+class Map {
+  groupBy(items: Iterable, callbackfn: (value: any, index: number) => key): Map<key, Array<mixed>>;
+}
+```
+[*CommonJS entry points:*](#commonjs-api)
+```
+core-js/proposals/array-grouping-v2
+core-js(-pure)/full/map/group-by
+core-js(-pure)/full/object/group-by
+```
+[*Examples*](https://is.gd/3a0PbH):
+```js
+Object.groupBy([1, 2, 3, 4, 5], it => it % 2); // => { 1: [1, 3, 5], 0: [2, 4] }
+
+const map = Map.groupBy([1, 2, 3, 4, 5], it => it % 2);
+map.get(1); // => [1, 3, 5]
+map.get(0); // => [2, 4]
+````
 ##### [`AsyncIterator` helpers](https://github.com/tc39/proposal-async-iterator-helpers)[⬆](#index)
 Modules [`esnext.async-iterator.constructor`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.async-iterator.constructor.js), [`esnext.async-iterator.drop`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.async-iterator.drop.js), [`esnext.async-iterator.every`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.async-iterator.every.js), [`esnext.async-iterator.filter`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.async-iterator.filter.js), [`esnext.async-iterator.find`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.async-iterator.find.js), [`esnext.async-iterator.flat-map`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.async-iterator.flat-map.js), [`esnext.async-iterator.for-each`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.async-iterator.for-each.js), [`esnext.async-iterator.from`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.async-iterator.from.js), [`esnext.async-iterator.map`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.async-iterator.map.js), [`esnext.async-iterator.reduce`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.async-iterator.reduce.js), [`esnext.async-iterator.some`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.async-iterator.some.js), [`esnext.async-iterator.take`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.async-iterator.take.js), [`esnext.async-iterator.to-array`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.async-iterator.to-array.js), , [`esnext.iterator.to-async`](https://github.com/zloirock/core-js/blob/master/packages/core-js/modules/esnext.iterator.to-async.js)
 ```js
diff --git a/packages/core-js-compat/src/data.mjs b/packages/core-js-compat/src/data.mjs
index f53de9676bfe..e24f9f33a3e2 100644
--- a/packages/core-js-compat/src/data.mjs
+++ b/packages/core-js-compat/src/data.mjs
@@ -1878,7 +1878,7 @@ export const data = {
     // bun: '0.1.9',
     // https://github.com/tc39/proposal-array-grouping/issues/44#issuecomment-1306311107
     // chrome: '108',
-    safari: '16.4',
+    // safari: '16.4',
   },
   // TODO: Remove from `core-js@4`
   'esnext.array.group-by': {
@@ -1891,7 +1891,7 @@ export const data = {
     // bun: '0.1.9',
     // https://github.com/tc39/proposal-array-grouping/issues/44#issuecomment-1306311107
     // chrome: '108',
-    safari: '16.4',
+    // safari: '16.4',
   },
   'esnext.array.is-template-object': {
   },
@@ -2112,6 +2112,8 @@ export const data = {
   // TODO: Remove from `core-js@4`
   'esnext.object.iterate-values': {
   },
+  'esnext.object.group-by': {
+  },
   // TODO: Remove this module from `core-js@4` since it's split to modules listed below
   'esnext.observable': {
   },
diff --git a/packages/core-js-compat/src/modules-by-versions.mjs b/packages/core-js-compat/src/modules-by-versions.mjs
index f13b1820a067..c3b7b76b082d 100644
--- a/packages/core-js-compat/src/modules-by-versions.mjs
+++ b/packages/core-js-compat/src/modules-by-versions.mjs
@@ -206,6 +206,7 @@ export default {
     'es.string.is-well-formed',
     'es.string.to-well-formed',
     'esnext.function.metadata',
+    'esnext.object.group-by',
     'esnext.promise.with-resolvers',
     'esnext.symbol.is-registered-symbol',
     'esnext.symbol.is-well-known-symbol',
diff --git a/packages/core-js/full/object/group-by.js b/packages/core-js/full/object/group-by.js
new file mode 100644
index 000000000000..fade84f64662
--- /dev/null
+++ b/packages/core-js/full/object/group-by.js
@@ -0,0 +1,6 @@
+require('../../modules/es.object.create');
+require('../../modules/esnext.object.group-by');
+
+var path = require('../../internals/path');
+
+module.exports = path.Object.groupBy;
diff --git a/packages/core-js/full/object/index.js b/packages/core-js/full/object/index.js
index 576c404e6a70..fb7fbc037115 100644
--- a/packages/core-js/full/object/index.js
+++ b/packages/core-js/full/object/index.js
@@ -1,4 +1,5 @@
 var parent = require('../../actual/object');
+require('../../modules/esnext.object.group-by');
 // TODO: Remove from `core-js@4`
 require('../../modules/esnext.object.has-own');
 require('../../modules/esnext.object.iterate-entries');
diff --git a/packages/core-js/modules/esnext.map.group-by.js b/packages/core-js/modules/esnext.map.group-by.js
index 0a68f6d6a838..5d7c6b7a899f 100644
--- a/packages/core-js/modules/esnext.map.group-by.js
+++ b/packages/core-js/modules/esnext.map.group-by.js
@@ -1,29 +1,30 @@
 'use strict';
 var $ = require('../internals/export');
-var call = require('../internals/function-call');
 var uncurryThis = require('../internals/function-uncurry-this');
-var isCallable = require('../internals/is-callable');
 var aCallable = require('../internals/a-callable');
+var requireObjectCoercible = require('../internals/require-object-coercible');
 var iterate = require('../internals/iterate');
-var Map = require('../internals/map-helpers').Map;
+var MapHelpers = require('../internals/map-helpers');
 
+var Map = MapHelpers.Map;
+var has = MapHelpers.has;
+var get = MapHelpers.get;
+var set = MapHelpers.set;
 var push = uncurryThis([].push);
 
 // `Map.groupBy` method
-// https://github.com/tc39/proposal-collection-methods
+// https://github.com/tc39/proposal-array-grouping
 $({ target: 'Map', stat: true, forced: true }, {
-  groupBy: function groupBy(iterable, keyDerivative) {
-    var C = isCallable(this) ? this : Map;
-    var newMap = new C();
-    aCallable(keyDerivative);
-    var has = aCallable(newMap.has);
-    var get = aCallable(newMap.get);
-    var set = aCallable(newMap.set);
-    iterate(iterable, function (element) {
-      var derivedKey = keyDerivative(element);
-      if (!call(has, newMap, derivedKey)) call(set, newMap, derivedKey, [element]);
-      else push(call(get, newMap, derivedKey), element);
+  groupBy: function groupBy(items, callbackfn) {
+    requireObjectCoercible(items);
+    aCallable(callbackfn);
+    var map = new Map();
+    var k = 0;
+    iterate(items, function (value) {
+      var key = callbackfn(value, k++);
+      if (!has(map, key)) set(map, key, [value]);
+      else push(get(map, key), value);
     });
-    return newMap;
+    return map;
   }
 });
diff --git a/packages/core-js/modules/esnext.object.group-by.js b/packages/core-js/modules/esnext.object.group-by.js
new file mode 100644
index 000000000000..d84a1b529478
--- /dev/null
+++ b/packages/core-js/modules/esnext.object.group-by.js
@@ -0,0 +1,29 @@
+'use strict';
+var $ = require('../internals/export');
+var getBuiltIn = require('../internals/get-built-in');
+var uncurryThis = require('../internals/function-uncurry-this');
+var aCallable = require('../internals/a-callable');
+var requireObjectCoercible = require('../internals/require-object-coercible');
+var has = require('../internals/has-own-property');
+var toPropertyKey = require('../internals/to-property-key');
+var iterate = require('../internals/iterate');
+
+var create = getBuiltIn('Object', 'create');
+var push = uncurryThis([].push);
+
+// `Object.groupBy` method
+// https://github.com/tc39/proposal-array-grouping
+$({ target: 'Object', stat: true, forced: true }, {
+  groupBy: function groupBy(items, callbackfn) {
+    requireObjectCoercible(items);
+    aCallable(callbackfn);
+    var obj = create(null);
+    var k = 0;
+    iterate(items, function (value) {
+      var key = toPropertyKey(callbackfn(value, k++));
+      if (!has(obj, key)) obj[key] = [value];
+      else push(obj[key], value);
+    });
+    return obj;
+  }
+});
diff --git a/packages/core-js/proposals/array-grouping-v2.js b/packages/core-js/proposals/array-grouping-v2.js
new file mode 100644
index 000000000000..5fb0286238b4
--- /dev/null
+++ b/packages/core-js/proposals/array-grouping-v2.js
@@ -0,0 +1,3 @@
+// https://github.com/tc39/proposal-array-grouping
+require('../modules/esnext.map.group-by');
+require('../modules/esnext.object.group-by');
diff --git a/packages/core-js/stage/2.js b/packages/core-js/stage/2.js
index 07c6591b2718..a77902975af1 100644
--- a/packages/core-js/stage/2.js
+++ b/packages/core-js/stage/2.js
@@ -1,5 +1,6 @@
 var parent = require('./3');
 
+require('../proposals/array-grouping-v2');
 require('../proposals/array-is-template-object');
 require('../proposals/async-explicit-resource-management');
 require('../proposals/async-iterator-helpers');
diff --git a/packages/core-js/stage/3.js b/packages/core-js/stage/3.js
index e34fe20a18bc..e92ffea63c20 100644
--- a/packages/core-js/stage/3.js
+++ b/packages/core-js/stage/3.js
@@ -1,7 +1,6 @@
 var parent = require('./4');
 
 require('../proposals/array-from-async-stage-2');
-require('../proposals/array-grouping-stage-3-2');
 require('../proposals/array-buffer-transfer');
 require('../proposals/decorator-metadata-v2');
 require('../proposals/explicit-resource-management');
@@ -10,6 +9,7 @@ require('../proposals/json-parse-with-source');
 require('../proposals/set-methods-v2');
 // TODO: Obsolete versions, remove from `core-js@4`
 require('../proposals/array-grouping-stage-3');
+require('../proposals/array-grouping-stage-3-2');
 require('../proposals/change-array-by-copy');
 require('../proposals/iterator-helpers-stage-3');
 
diff --git a/tests/compat/tests.js b/tests/compat/tests.js
index 5a72572ba51d..894431759065 100644
--- a/tests/compat/tests.js
+++ b/tests/compat/tests.js
@@ -1690,6 +1690,9 @@ GLOBAL.tests = {
   'esnext.number.from-string': function () {
     return Number.fromString;
   },
+  'esnext.object.group-by': function () {
+    return Object.groupBy;
+  },
   // TODO: Remove this module from `core-js@4` since it's split to modules listed below
   'esnext.observable': function () {
     return Observable;
diff --git a/tests/entries/unit.mjs b/tests/entries/unit.mjs
index 9a66513c5977..20c5c403e857 100644
--- a/tests/entries/unit.mjs
+++ b/tests/entries/unit.mjs
@@ -797,6 +797,7 @@ for (PATH of ['core-js-pure', 'core-js']) {
     ok(typeof load(NS, 'object/iterate-entries')({}).next == 'function');
     ok(typeof load(NS, 'object/iterate-keys')({}).next == 'function');
     ok(typeof load(NS, 'object/iterate-values')({}).next == 'function');
+    ok(load(NS, 'object/group-by')([1, 2, 3, 4, 5], it => it % 2 === 0 ? 'even' : 'odd').odd.length === 3);
     ok('from' in load(NS, 'observable'));
     ok(typeof load(NS, 'reflect/define-metadata') == 'function');
     ok(typeof load(NS, 'reflect/delete-metadata') == 'function');
@@ -896,6 +897,7 @@ for (PATH of ['core-js-pure', 'core-js']) {
   load('proposals/array-grouping');
   load('proposals/array-grouping-stage-3');
   load('proposals/array-grouping-stage-3-2');
+  load('proposals/array-grouping-v2');
   load('proposals/array-includes');
   load('proposals/array-is-template-object');
   load('proposals/array-last');
diff --git a/tests/unit-global/esnext.map.group-by.js b/tests/unit-global/esnext.map.group-by.js
index 024d0921e1d0..7453dc0cc322 100644
--- a/tests/unit-global/esnext.map.group-by.js
+++ b/tests/unit-global/esnext.map.group-by.js
@@ -12,13 +12,15 @@ QUnit.test('Map.groupBy', assert => {
 
   assert.true(Map.groupBy([], it => it) instanceof Map);
 
-  assert.deepEqual(toArray(Map.groupBy([], it => it)), []);
-  assert.deepEqual(toArray(Map.groupBy([1, 2], it => it ** 2)), [[1, [1]], [4, [2]]]);
-  assert.deepEqual(toArray(Map.groupBy([1, 2, 1], it => it ** 2)), [[1, [1, 1]], [4, [2]]]);
-  assert.deepEqual(toArray(Map.groupBy(createIterable([1, 2]), it => it ** 2)), [[1, [1]], [4, [2]]]);
+  assert.deepEqual(toArray(groupBy([], it => it)), []);
+  assert.deepEqual(toArray(groupBy([1, 2], it => it ** 2)), [[1, [1]], [4, [2]]]);
+  assert.deepEqual(toArray(groupBy([1, 2, 1], it => it ** 2)), [[1, [1, 1]], [4, [2]]]);
+  assert.deepEqual(toArray(groupBy(createIterable([1, 2]), it => it ** 2)), [[1, [1]], [4, [2]]]);
 
   const element = {};
-  Map.groupBy([element], it => assert.same(it, element));
-
-  // assert.throws(() => groupBy([1, 2], it => it));
+  groupBy([element], function (it, i) {
+    assert.same(arguments.length, 2);
+    assert.same(it, element);
+    assert.same(i, 0);
+  });
 });
diff --git a/tests/unit-global/esnext.object.group-by.js b/tests/unit-global/esnext.object.group-by.js
new file mode 100644
index 000000000000..7959737d0f37
--- /dev/null
+++ b/tests/unit-global/esnext.object.group-by.js
@@ -0,0 +1,25 @@
+import { createIterable } from '../helpers/helpers';
+
+QUnit.test('Object.groupBy', assert => {
+  const { groupBy, getPrototypeOf, entries } = Object;
+
+  assert.isFunction(groupBy);
+  assert.arity(groupBy, 2);
+  assert.name(groupBy, 'groupBy');
+  assert.looksNative(groupBy);
+  assert.nonEnumerable(Object, 'groupBy');
+
+  assert.same(getPrototypeOf(groupBy([], it => it)), null);
+
+  assert.deepEqual(entries(groupBy([], it => it)), []);
+  assert.deepEqual(entries(groupBy([1, 2], it => it ** 2)), [['1', [1]], ['4', [2]]]);
+  assert.deepEqual(entries(groupBy([1, 2, 1], it => it ** 2)), [['1', [1, 1]], ['4', [2]]]);
+  assert.deepEqual(entries(groupBy(createIterable([1, 2]), it => it ** 2)), [['1', [1]], ['4', [2]]]);
+
+  const element = {};
+  groupBy([element], function (it, i) {
+    assert.same(arguments.length, 2);
+    assert.same(it, element);
+    assert.same(i, 0);
+  });
+});
diff --git a/tests/unit-pure/esnext.map.group-by.js b/tests/unit-pure/esnext.map.group-by.js
index 5271ce02872e..4ebd9ee206ec 100644
--- a/tests/unit-pure/esnext.map.group-by.js
+++ b/tests/unit-pure/esnext.map.group-by.js
@@ -10,15 +10,17 @@ QUnit.test('Map.groupBy', assert => {
   assert.arity(groupBy, 2);
   assert.name(groupBy, 'groupBy');
 
-  assert.true(Map.groupBy([], it => it) instanceof Map);
+  assert.true(groupBy([], it => it) instanceof Map);
 
-  assert.deepEqual(from(Map.groupBy([], it => it)), []);
-  assert.deepEqual(from(Map.groupBy([1, 2], it => it ** 2)), [[1, [1]], [4, [2]]]);
-  assert.deepEqual(from(Map.groupBy([1, 2, 1], it => it ** 2)), [[1, [1, 1]], [4, [2]]]);
-  assert.deepEqual(from(Map.groupBy(createIterable([1, 2]), it => it ** 2)), [[1, [1]], [4, [2]]]);
+  assert.deepEqual(from(groupBy([], it => it)), []);
+  assert.deepEqual(from(groupBy([1, 2], it => it ** 2)), [[1, [1]], [4, [2]]]);
+  assert.deepEqual(from(groupBy([1, 2, 1], it => it ** 2)), [[1, [1, 1]], [4, [2]]]);
+  assert.deepEqual(from(groupBy(createIterable([1, 2]), it => it ** 2)), [[1, [1]], [4, [2]]]);
 
   const element = {};
-  Map.groupBy([element], it => assert.same(it, element));
-
-  // assert.throws(() => groupBy([1, 2], it => it));
+  groupBy([element], function (it, i) {
+    assert.same(arguments.length, 2);
+    assert.same(it, element);
+    assert.same(i, 0);
+  });
 });
diff --git a/tests/unit-pure/esnext.object.group-by.js b/tests/unit-pure/esnext.object.group-by.js
new file mode 100644
index 000000000000..74b5aadbf61f
--- /dev/null
+++ b/tests/unit-pure/esnext.object.group-by.js
@@ -0,0 +1,24 @@
+import { createIterable } from '../helpers/helpers';
+import groupBy from 'core-js-pure/full/object/group-by';
+import getPrototypeOf from 'core-js-pure/es/object/get-prototype-of';
+import entries from 'core-js-pure/es/object/entries';
+
+QUnit.test('Object.groupBy', assert => {
+  assert.isFunction(groupBy);
+  assert.arity(groupBy, 2);
+  assert.name(groupBy, 'groupBy');
+
+  assert.same(getPrototypeOf(groupBy([], it => it)), null);
+
+  assert.deepEqual(entries(groupBy([], it => it)), []);
+  assert.deepEqual(entries(groupBy([1, 2], it => it ** 2)), [['1', [1]], ['4', [2]]]);
+  assert.deepEqual(entries(groupBy([1, 2, 1], it => it ** 2)), [['1', [1, 1]], ['4', [2]]]);
+  assert.deepEqual(entries(groupBy(createIterable([1, 2]), it => it ** 2)), [['1', [1]], ['4', [2]]]);
+
+  const element = {};
+  groupBy([element], function (it, i) {
+    assert.same(arguments.length, 2);
+    assert.same(it, element);
+    assert.same(i, 0);
+  });
+});