v8/src/array-iterator.js

// Copyright 2013 the V8 project authors. All rights reserved.
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// modification, are permitted provided that the following conditions are
// met:
//
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//       with the distribution.
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'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();