es.symbol.js

'use strict';
var $ = require('../internals/export');
var global = require('../internals/global');
var getBuiltIn = require('../internals/get-built-in');
var IS_PURE = require('../internals/is-pure');
var DESCRIPTORS = require('../internals/descriptors');
var NATIVE_SYMBOL = require('../internals/native-symbol');
var fails = require('../internals/fails');
var has = require('../internals/has');
var isArray = require('../internals/is-array');
var isObject = require('../internals/is-object');
var anObject = require('../internals/an-object');
var toObject = require('../internals/to-object');
var toIndexedObject = require('../internals/to-indexed-object');
var toPrimitive = require('../internals/to-primitive');
var createPropertyDescriptor = require('../internals/create-property-descriptor');
var nativeObjectCreate = require('../internals/object-create');
var objectKeys = require('../internals/object-keys');
var getOwnPropertyNamesModule = require('../internals/object-get-own-property-names');
var getOwnPropertyNamesExternal = require('../internals/object-get-own-property-names-external');
var getOwnPropertySymbolsModule = require('../internals/object-get-own-property-symbols');
var getOwnPropertyDescriptorModule = require('../internals/object-get-own-property-descriptor');
var definePropertyModule = require('../internals/object-define-property');
var propertyIsEnumerableModule = require('../internals/object-property-is-enumerable');
var createNonEnumerableProperty = require('../internals/create-non-enumerable-property');
var redefine = require('../internals/redefine');
var shared = require('../internals/shared');
var sharedKey = require('../internals/shared-key');
var hiddenKeys = require('../internals/hidden-keys');
var uid = require('../internals/uid');
var wellKnownSymbol = require('../internals/well-known-symbol');
var wrappedWellKnownSymbolModule = require('../internals/wrapped-well-known-symbol');
var defineWellKnownSymbol = require('../internals/define-well-known-symbol');
var setToStringTag = require('../internals/set-to-string-tag');
var InternalStateModule = require('../internals/internal-state');
var $forEach = require('../internals/array-iteration').forEach;

var HIDDEN = sharedKey('hidden');
var SYMBOL = 'Symbol';
var PROTOTYPE = 'prototype';
var TO_PRIMITIVE = wellKnownSymbol('toPrimitive');
var setInternalState = InternalStateModule.set;
var getInternalState = InternalStateModule.getterFor(SYMBOL);
var ObjectPrototype = Object[PROTOTYPE];
var $Symbol = global.Symbol;
var $stringify = getBuiltIn('JSON', 'stringify');
var nativeGetOwnPropertyDescriptor = getOwnPropertyDescriptorModule.f;
var nativeDefineProperty = definePropertyModule.f;
var nativeGetOwnPropertyNames = getOwnPropertyNamesExternal.f;
var nativePropertyIsEnumerable = propertyIsEnumerableModule.f;
var AllSymbols = shared('symbols');
var ObjectPrototypeSymbols = shared('op-symbols');
var StringToSymbolRegistry = shared('string-to-symbol-registry');
var SymbolToStringRegistry = shared('symbol-to-string-registry');
var WellKnownSymbolsStore = shared('wks');
var QObject = global.QObject;
// Don't use setters in Qt Script, https://github.com/zloirock/core-js/issues/173
var USE_SETTER = !QObject || !QObject[PROTOTYPE] || !QObject[PROTOTYPE].findChild;

// fallback for old Android, https://code.google.com/p/v8/issues/detail?id=687
var setSymbolDescriptor = DESCRIPTORS && fails(function () {
  return nativeObjectCreate(nativeDefineProperty({}, 'a', {
    get: function () { return nativeDefineProperty(this, 'a', { value: 7 }).a; }
  })).a != 7;
}) ? function (O, P, Attributes) {
  var ObjectPrototypeDescriptor = nativeGetOwnPropertyDescriptor(ObjectPrototype, P);
  if (ObjectPrototypeDescriptor) delete ObjectPrototype[P];
  nativeDefineProperty(O, P, Attributes);
  if (ObjectPrototypeDescriptor && O !== ObjectPrototype) {
    nativeDefineProperty(ObjectPrototype, P, ObjectPrototypeDescriptor);
  }
} : nativeDefineProperty;

var wrap = function (tag, description) {
  var symbol = AllSymbols[tag] = nativeObjectCreate($Symbol[PROTOTYPE]);
  setInternalState(symbol, {
    type: SYMBOL,
    tag: tag,
    description: description
  });
  if (!DESCRIPTORS) symbol.description = description;
  return symbol;
};

var isSymbol = NATIVE_SYMBOL && typeof $Symbol.iterator == 'symbol' ? function (it) {
  return typeof it == 'symbol';
} : function (it) {
  return Object(it) instanceof $Symbol;
};

var $defineProperty = function defineProperty(O, P, Attributes) {
  if (O === ObjectPrototype) $defineProperty(ObjectPrototypeSymbols, P, Attributes);
  anObject(O);
  var key = toPrimitive(P, true);
  anObject(Attributes);
  if (has(AllSymbols, key)) {
    if (!Attributes.enumerable) {
      if (!has(O, HIDDEN)) nativeDefineProperty(O, HIDDEN, createPropertyDescriptor(1, {}));
      O[HIDDEN][key] = true;
    } else {
      if (has(O, HIDDEN) && O[HIDDEN][key]) O[HIDDEN][key] = false;
      Attributes = nativeObjectCreate(Attributes, { enumerable: createPropertyDescriptor(0, false) });
    } return setSymbolDescriptor(O, key, Attributes);
  } return nativeDefineProperty(O, key, Attributes);
};

var $defineProperties = function defineProperties(O, Properties) {
  anObject(O);
  var properties = toIndexedObject(Properties);
  var keys = objectKeys(properties).concat($getOwnPropertySymbols(properties));
  $forEach(keys, function (key) {
    if (!DESCRIPTORS || $propertyIsEnumerable.call(properties, key)) $defineProperty(O, key, properties[key]);
  });
  return O;
};

var $create = function create(O, Properties) {
  return Properties === undefined ? nativeObjectCreate(O) : $defineProperties(nativeObjectCreate(O), Properties);
};

var $propertyIsEnumerable = function propertyIsEnumerable(V) {
  var P = toPrimitive(V, true);
  var enumerable = nativePropertyIsEnumerable.call(this, P);
  if (this === ObjectPrototype && has(AllSymbols, P) && !has(ObjectPrototypeSymbols, P)) return false;
  return enumerable || !has(this, P) || !has(AllSymbols, P) || has(this, HIDDEN) && this[HIDDEN][P] ? enumerable : true;
};

var $getOwnPropertyDescriptor = function getOwnPropertyDescriptor(O, P) {
  var it = toIndexedObject(O);
  var key = toPrimitive(P, true);
  if (it === ObjectPrototype && has(AllSymbols, key) && !has(ObjectPrototypeSymbols, key)) return;
  var descriptor = nativeGetOwnPropertyDescriptor(it, key);
  if (descriptor && has(AllSymbols, key) && !(has(it, HIDDEN) && it[HIDDEN][key])) {
    descriptor.enumerable = true;
  }
  return descriptor;
};

var $getOwnPropertyNames = function getOwnPropertyNames(O) {
  var names = nativeGetOwnPropertyNames(toIndexedObject(O));
  var result = [];
  $forEach(names, function (key) {
    if (!has(AllSymbols, key) && !has(hiddenKeys, key)) result.push(key);
  });
  return result;
};

var $getOwnPropertySymbols = function getOwnPropertySymbols(O) {
  var IS_OBJECT_PROTOTYPE = O === ObjectPrototype;
  var names = nativeGetOwnPropertyNames(IS_OBJECT_PROTOTYPE ? ObjectPrototypeSymbols : toIndexedObject(O));
  var result = [];
  $forEach(names, function (key) {
    if (has(AllSymbols, key) && (!IS_OBJECT_PROTOTYPE || has(ObjectPrototype, key))) {
      result.push(AllSymbols[key]);
    }
  });
  return result;
};

// `Symbol` constructor
// https://tc39.github.io/ecma262/#sec-symbol-constructor
if (!NATIVE_SYMBOL) {
  $Symbol = function Symbol() {
    if (this instanceof $Symbol) throw TypeError('Symbol is not a constructor');
    var description = !arguments.length || arguments[0] === undefined ? undefined : String(arguments[0]);
    var tag = uid(description);
    var setter = function (value) {
      if (this === ObjectPrototype) setter.call(ObjectPrototypeSymbols, value);
      if (has(this, HIDDEN) && has(this[HIDDEN], tag)) this[HIDDEN][tag] = false;
      setSymbolDescriptor(this, tag, createPropertyDescriptor(1, value));
    };
    if (DESCRIPTORS && USE_SETTER) setSymbolDescriptor(ObjectPrototype, tag, { configurable: true, set: setter });
    return wrap(tag, description);
  };

  redefine($Symbol[PROTOTYPE], 'toString', function toString() {
    return getInternalState(this).tag;
  });

  propertyIsEnumerableModule.f = $propertyIsEnumerable;
  definePropertyModule.f = $defineProperty;
  getOwnPropertyDescriptorModule.f = $getOwnPropertyDescriptor;
  getOwnPropertyNamesModule.f = getOwnPropertyNamesExternal.f = $getOwnPropertyNames;
  getOwnPropertySymbolsModule.f = $getOwnPropertySymbols;

  if (DESCRIPTORS) {
    // https://github.com/tc39/proposal-Symbol-description
    nativeDefineProperty($Symbol[PROTOTYPE], 'description', {
      configurable: true,
      get: function description() {
        return getInternalState(this).description;
      }
    });
    if (!IS_PURE) {
      redefine(ObjectPrototype, 'propertyIsEnumerable', $propertyIsEnumerable, { unsafe: true });
    }
  }

  wrappedWellKnownSymbolModule.f = function (name) {
    return wrap(wellKnownSymbol(name), name);
  };
}

$({ global: true, wrap: true, forced: !NATIVE_SYMBOL, sham: !NATIVE_SYMBOL }, {
  Symbol: $Symbol
});

$forEach(objectKeys(WellKnownSymbolsStore), function (name) {
  defineWellKnownSymbol(name);
});

$({ target: SYMBOL, stat: true, forced: !NATIVE_SYMBOL }, {
  // `Symbol.for` method
  // https://tc39.github.io/ecma262/#sec-symbol.for
  'for': function (key) {
    var string = String(key);
    if (has(StringToSymbolRegistry, string)) return StringToSymbolRegistry[string];
    var symbol = $Symbol(string);
    StringToSymbolRegistry[string] = symbol;
    SymbolToStringRegistry[symbol] = string;
    return symbol;
  },
  // `Symbol.keyFor` method
  // https://tc39.github.io/ecma262/#sec-symbol.keyfor
  keyFor: function keyFor(sym) {
    if (!isSymbol(sym)) throw TypeError(sym + ' is not a symbol');
    if (has(SymbolToStringRegistry, sym)) return SymbolToStringRegistry[sym];
  },
  useSetter: function () { USE_SETTER = true; },
  useSimple: function () { USE_SETTER = false; }
});

$({ target: 'Object', stat: true, forced: !NATIVE_SYMBOL, sham: !DESCRIPTORS }, {
  // `Object.create` method
  // https://tc39.github.io/ecma262/#sec-object.create
  create: $create,
  // `Object.defineProperty` method
  // https://tc39.github.io/ecma262/#sec-object.defineproperty
  defineProperty: $defineProperty,
  // `Object.defineProperties` method
  // https://tc39.github.io/ecma262/#sec-object.defineproperties
  defineProperties: $defineProperties,
  // `Object.getOwnPropertyDescriptor` method
  // https://tc39.github.io/ecma262/#sec-object.getownpropertydescriptors
  getOwnPropertyDescriptor: $getOwnPropertyDescriptor
});

$({ target: 'Object', stat: true, forced: !NATIVE_SYMBOL }, {
  // `Object.getOwnPropertyNames` method
  // https://tc39.github.io/ecma262/#sec-object.getownpropertynames
  getOwnPropertyNames: $getOwnPropertyNames,
  // `Object.getOwnPropertySymbols` method
  // https://tc39.github.io/ecma262/#sec-object.getownpropertysymbols
  getOwnPropertySymbols: $getOwnPropertySymbols
});

// Chrome 38 and 39 `Object.getOwnPropertySymbols` fails on primitives
// https://bugs.chromium.org/p/v8/issues/detail?id=3443
$({ target: 'Object', stat: true, forced: fails(function () { getOwnPropertySymbolsModule.f(1); }) }, {
  getOwnPropertySymbols: function getOwnPropertySymbols(it) {
    return getOwnPropertySymbolsModule.f(toObject(it));
  }
});

// `JSON.stringify` method behavior with symbols
// https://tc39.github.io/ecma262/#sec-json.stringify
if ($stringify) {
  var FORCED_JSON_STRINGIFY = !NATIVE_SYMBOL || fails(function () {
    var symbol = $Symbol();
    // MS Edge converts symbol values to JSON as {}
    return $stringify([symbol]) != '[null]'
      // WebKit converts symbol values to JSON as null
      || $stringify({ a: symbol }) != '{}'
      // V8 throws on boxed symbols
      || $stringify(Object(symbol)) != '{}';
  });

  $({ target: 'JSON', stat: true, forced: FORCED_JSON_STRINGIFY }, {
    // eslint-disable-next-line no-unused-vars
    stringify: function stringify(it, replacer, space) {
      var args = [it];
      var index = 1;
      var $replacer;
      while (arguments.length > index) args.push(arguments[index++]);
      $replacer = replacer;
      if (!isObject(replacer) && it === undefined || isSymbol(it)) return; // IE8 returns string on undefined
      if (!isArray(replacer)) replacer = function (key, value) {
        if (typeof $replacer == 'function') value = $replacer.call(this, key, value);
        if (!isSymbol(value)) return value;
      };
      args[1] = replacer;
      return $stringify.apply(null, args);
    }
  });
}

// `Symbol.prototype[@@toPrimitive]` method
// https://tc39.github.io/ecma262/#sec-symbol.prototype-@@toprimitive
if (!$Symbol[PROTOTYPE][TO_PRIMITIVE]) {
  createNonEnumerableProperty($Symbol[PROTOTYPE], TO_PRIMITIVE, $Symbol[PROTOTYPE].valueOf);
}
// `Symbol.prototype[@@toStringTag]` property
// https://tc39.github.io/ecma262/#sec-symbol.prototype-@@tostringtag
setToStringTag($Symbol, SYMBOL);

hiddenKeys[HIDDEN] = true;