michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 'use strict';
michael@0: 
michael@0: module.metadata = {
michael@0:   "stability": "experimental"
michael@0: };
michael@0: 
michael@0: // This is known as @@iterator in the ES6 spec.  Until it is bound to
michael@0: // some well-known name, find the @@iterator object by expecting it as
michael@0: // the first property accessed on a for-of iterable.
michael@0: const iteratorSymbol = (function() {
michael@0:   try {
michael@0:     for (var _ of Proxy.create({get: function(_, name) { throw name; } }))
michael@0:       break;
michael@0:   } catch (name) {
michael@0:     return name;
michael@0:   }
michael@0:   throw new TypeError;
michael@0: })();
michael@0: 
michael@0: exports.iteratorSymbol = iteratorSymbol;
michael@0: 
michael@0: // An adaptor that, given an object that is iterable with for-of, is
michael@0: // suitable for being bound to __iterator__ in order to make the object
michael@0: // iterable in the same way via for-in.
michael@0: function forInIterator() {
michael@0:     for (let item of this)
michael@0:         yield item;
michael@0: }
michael@0: 
michael@0: exports.forInIterator = forInIterator;