core-js/internals/define-iterator.js

'use strict';
var $ = require('../internals/export');
var createIteratorConstructor = require('../internals/create-iterator-constructor');
var getPrototypeOf = require('../internals/object-get-prototype-of');
var setPrototypeOf = require('../internals/object-set-prototype-of');
var setToStringTag = require('../internals/set-to-string-tag');
var createNonEnumerableProperty = require('../internals/create-non-enumerable-property');
var redefine = require('../internals/redefine');
var wellKnownSymbol = require('../internals/well-known-symbol');
var IS_PURE = require('../internals/is-pure');
var Iterators = require('../internals/iterators');
var IteratorsCore = require('../internals/iterators-core');

var IteratorPrototype = IteratorsCore.IteratorPrototype;
var BUGGY_SAFARI_ITERATORS = IteratorsCore.BUGGY_SAFARI_ITERATORS;
var ITERATOR = wellKnownSymbol('iterator');
var KEYS = 'keys';
var VALUES = 'values';
var ENTRIES = 'entries';

var returnThis = function () { return this; };

module.exports = function (Iterable, NAME, IteratorConstructor, next, DEFAULT, IS_SET, FORCED) {
  createIteratorConstructor(IteratorConstructor, NAME, next);

  var getIterationMethod = function (KIND) {
    if (KIND === DEFAULT && defaultIterator) return defaultIterator;
    if (!BUGGY_SAFARI_ITERATORS && KIND in IterablePrototype) return IterablePrototype[KIND];
    switch (KIND) {
      case KEYS: return function keys() { return new IteratorConstructor(this, KIND); };
      case VALUES: return function values() { return new IteratorConstructor(this, KIND); };
      case ENTRIES: return function entries() { return new IteratorConstructor(this, KIND); };
    } return function () { return new IteratorConstructor(this); };
  };

  var TO_STRING_TAG = NAME + ' Iterator';
  var INCORRECT_VALUES_NAME = false;
  var IterablePrototype = Iterable.prototype;
  var nativeIterator = IterablePrototype[ITERATOR]
    || IterablePrototype['@@iterator']
    || DEFAULT && IterablePrototype[DEFAULT];
  var defaultIterator = !BUGGY_SAFARI_ITERATORS && nativeIterator || getIterationMethod(DEFAULT);
  var anyNativeIterator = NAME == 'Array' ? IterablePrototype.entries || nativeIterator : nativeIterator;
  var CurrentIteratorPrototype, methods, KEY;

  // fix native
  if (anyNativeIterator) {
    CurrentIteratorPrototype = getPrototypeOf(anyNativeIterator.call(new Iterable()));
    if (IteratorPrototype !== Object.prototype && CurrentIteratorPrototype.next) {
      if (!IS_PURE && getPrototypeOf(CurrentIteratorPrototype) !== IteratorPrototype) {
        if (setPrototypeOf) {
          setPrototypeOf(CurrentIteratorPrototype, IteratorPrototype);
        } else if (typeof CurrentIteratorPrototype[ITERATOR] != 'function') {
          createNonEnumerableProperty(CurrentIteratorPrototype, ITERATOR, returnThis);
        }
      }
      // Set @@toStringTag to native iterators
      setToStringTag(CurrentIteratorPrototype, TO_STRING_TAG, true, true);
      if (IS_PURE) Iterators[TO_STRING_TAG] = returnThis;
    }
  }

  // fix Array#{values, @@iterator}.name in V8 / FF
  if (DEFAULT == VALUES && nativeIterator && nativeIterator.name !== VALUES) {
    INCORRECT_VALUES_NAME = true;
    defaultIterator = function values() { return nativeIterator.call(this); };
  }

  // define iterator
  if ((!IS_PURE || FORCED) && IterablePrototype[ITERATOR] !== defaultIterator) {
    createNonEnumerableProperty(IterablePrototype, ITERATOR, defaultIterator);
  }
  Iterators[NAME] = defaultIterator;

  // export additional methods
  if (DEFAULT) {
    methods = {
      values: getIterationMethod(VALUES),
      keys: IS_SET ? defaultIterator : getIterationMethod(KEYS),
      entries: getIterationMethod(ENTRIES)
    };
    if (FORCED) for (KEY in methods) {
      if (BUGGY_SAFARI_ITERATORS || INCORRECT_VALUES_NAME || !(KEY in IterablePrototype)) {
        redefine(IterablePrototype, KEY, methods[KEY]);
      }
    } else $({ target: NAME, proto: true, forced: BUGGY_SAFARI_ITERATORS || INCORRECT_VALUES_NAME }, methods);
  }

  return methods;
};