@@ -20,6 +20,19 @@
 
 var arrayPrototype = Array.prototype;
 
+// eslint-disable-next-line no-undef
+var iteratorSymbol = typeof Symbol != 'undefined' && Symbol.iterator;
+var iteratorPrototype = {};
+
+if (iteratorSymbol) {
+    // These iterators should themselves be iterable.
+    Object.defineProperty(iteratorPrototype, iteratorSymbol, {
+        value: function() {
+            return this;
+        }
+    });
+}
+
 [
     'join',
     'slice',
////////////////////////////////////////////////////////////////////////////
//
// Copyright 2016 Realm Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
////////////////////////////////////////////////////////////////////////////

'use strict';

var arrayPrototype = Array.prototype;

[
    'join',
    'slice',
    'forEach',
    'every',
    'some',
    'find',
    'findIndex',
    'map',
    'reduce',
    'reduceRight',
].forEach(function(methodName) {
    var method = arrayPrototype[methodName];
    if (method) {
        exports[methodName] = {value: method};
    }
});

['entries', 'keys', 'values'].forEach(function(methodName) {
    var method = function() {
        var self = this;
        var index = 0;

        return {
            next: function() {
                if (!self || index >= self.length) {
                    self = null;
                    return {done: true, value: undefined};
                }

                var value;
                switch (methodName) {
                    case 'entries':
                        value = [index, self[index]];
                        break;
                    case 'keys':
                        value = index;
                        break;
                    default:
                        value = self[index];
                }

                index++;
                return {done: false, value: value};
            }
        };
    };

    exports[methodName] = {value: method};
});

/* global Symbol */
if (typeof Symbol != 'undefined' && Symbol.iterator) {
    exports[Symbol.iterator] = exports.values;
}

maybe call this file collection-methods?