ES6: Array iterator methods

src/array-iterator.js

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// 'AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+'use strict';
+
+// This file relies on the fact that the following declaration has been made
+// in runtime.js:
+// var $Array = global.Array;
+
+var ARRAY_ITERATOR_KIND_KEYS = 1;
+var ARRAY_ITERATOR_KIND_VALUES = 2;
+var ARRAY_ITERATOR_KIND_ENTRIES = 3;
+// The spec draft also has "sparse" but it is never used.
+
+var iteratorObjectSymbol = %CreateSymbol(void 0);
+var arrayIteratorNextIndexSymbol = %CreateSymbol(void 0);
+var arrayIterationKindSymbol = %CreateSymbol(void 0);
+
+function ArrayIterator() {}
+
+// 15.4.5.1 CreateArrayIterator Abstract Operation
+function CreateArrayIterator(array, kind) {
+  var object = ToObject(array);
+  var iterator = new ArrayIterator;
+  iterator[iteratorObjectSymbol] = object;
+  iterator[arrayIteratorNextIndexSymbol] = 0;
+  iterator[arrayIterationKindSymbol] = kind;
+  return iterator;
+}
+
+// 15.19.4.3.4 CreateItrResultObject
+function CreateIteratorResultObject(value, done) {
+  return {value: value, done: done};
+}
+
+// 15.4.5.2.2 ArrayIterator.prototype.next( )
+function ArrayIteratorNext() {
+  var iterator = ToObject(this);
+  var array = iterator[iteratorObjectSymbol];
+  if (!array) {
+    throw MakeTypeError('incompatible_method_receiver',
+                        ['Array Iterator.prototype.next']);
+  }
+
+  var index = iterator[arrayIteratorNextIndexSymbol];
+  var itemKind = iterator[arrayIterationKindSymbol];
+  var length = TO_UINT32(array.length);
+
+  // "sparse" is never used.
+
+  if (index >= length) {
+    iterator[arrayIteratorNextIndexSymbol] = 1 / 0; // Infinity
+    return CreateIteratorResultObject(void 0, true);
+  }
+
+  var elementKey = ToString(index);
+  iterator[arrayIteratorNextIndexSymbol] = index + 1;
+
+  if (itemKind == ARRAY_ITERATOR_KIND_VALUES)
+    return CreateIteratorResultObject(array[elementKey], false);
+
+  if (itemKind == ARRAY_ITERATOR_KIND_ENTRIES)
+    return CreateIteratorResultObject([elementKey, array[elementKey]], false);
+
+  return CreateIteratorResultObject(elementKey, false);
+}
+
+function ArrayEntries() {
+  return CreateArrayIterator(this, ARRAY_ITERATOR_KIND_ENTRIES);
+}
+
+function ArrayValues() {
+  return CreateArrayIterator(this, ARRAY_ITERATOR_KIND_VALUES);
+}
+
+function ArrayKeys() {
+  return CreateArrayIterator(this, ARRAY_ITERATOR_KIND_KEYS);
+}
+
+function SetUpArrayIterator() {
+  %CheckIsBootstrapping();
+
+  %FunctionSetInstanceClassName(ArrayIterator, 'Array Iterator');
+  %FunctionSetReadOnlyPrototype(ArrayIterator);
+
+  InstallFunctions(ArrayIterator.prototype, DONT_ENUM, $Array(
+    'next', ArrayIteratorNext
+  ));
+}
+
+SetUpArrayIterator();
+
+function ExtendArrayPrototype() {
+  %CheckIsBootstrapping();
+
+  InstallFunctions($Array.prototype, DONT_ENUM, $Array(
+    'entries', ArrayEntries,
+    'values', ArrayValues,
+    'keys', ArrayKeys
+  ));
+}
+
+ExtendArrayPrototype();