es6.symbol.js

'use strict';
// ECMAScript 6 symbols shim
var $              = require('./_')
  , global         = require('./_global')
  , core           = require('./_core')
  , has            = require('./_has')
  , DESCRIPTORS    = require('./_descriptors')
  , $export        = require('./_export')
  , redefine       = require('./_redefine')
  , META           = require('./_meta').KEY
  , $fails         = require('./_fails')
  , shared         = require('./_shared')
  , setToStringTag = require('./_set-to-string-tag')
  , uid            = require('./_uid')
  , wks            = require('./_wks')
  , keyOf          = require('./_keyof')
  , $names         = require('./_get-names')
  , enumKeys       = require('./_enum-keys')
  , isArray        = require('./_is-array')
  , anObject       = require('./_an-object')
  , toIObject      = require('./_to-iobject')
  , createDesc     = require('./_property-desc')
  , getDesc        = $.getDesc
  , setDesc        = $.setDesc
  , _create        = $.create
  , getNames       = $names.get
  , $Symbol        = global.Symbol
  , $JSON          = global.JSON
  , _stringify     = $JSON && $JSON.stringify
  , setter         = false
  , HIDDEN         = wks('_hidden')
  , isEnum         = $.isEnum
  , SymbolRegistry = shared('symbol-registry')
  , AllSymbols     = shared('symbols')
  , ObjectProto    = Object.prototype
  , USE_NATIVE     = typeof $Symbol == 'function';

// fallback for old Android, https://code.google.com/p/v8/issues/detail?id=687
var setSymbolDesc = DESCRIPTORS && $fails(function(){
  return _create(setDesc({}, 'a', {
    get: function(){ return setDesc(this, 'a', {value: 7}).a; }
  })).a != 7;
}) ? function(it, key, D){
  var protoDesc = getDesc(ObjectProto, key);
  if(protoDesc)delete ObjectProto[key];
  setDesc(it, key, D);
  if(protoDesc && it !== ObjectProto)setDesc(ObjectProto, key, protoDesc);
} : setDesc;

var wrap = function(tag){
  var sym = AllSymbols[tag] = _create($Symbol.prototype);
  sym._k = tag;
  DESCRIPTORS && setter && setSymbolDesc(ObjectProto, tag, {
    configurable: true,
    set: function(value){
      if(has(this, HIDDEN) && has(this[HIDDEN], tag))this[HIDDEN][tag] = false;
      setSymbolDesc(this, tag, createDesc(1, value));
    }
  });
  return sym;
};

var isSymbol = function(it){
  return typeof it == 'symbol';
};

var $defineProperty = function defineProperty(it, key, D){
  if(D && has(AllSymbols, key)){
    if(!D.enumerable){
      if(!has(it, HIDDEN))setDesc(it, HIDDEN, createDesc(1, {}));
      it[HIDDEN][key] = true;
    } else {
      if(has(it, HIDDEN) && it[HIDDEN][key])it[HIDDEN][key] = false;
      D = _create(D, {enumerable: createDesc(0, false)});
    } return setSymbolDesc(it, key, D);
  } return setDesc(it, key, D);
};
var $defineProperties = function defineProperties(it, P){
  anObject(it);
  var keys = enumKeys(P = toIObject(P))
    , i    = 0
    , l = keys.length
    , key;
  while(l > i)$defineProperty(it, key = keys[i++], P[key]);
  return it;
};
var $create = function create(it, P){
  return P === undefined ? _create(it) : $defineProperties(_create(it), P);
};
var $propertyIsEnumerable = function propertyIsEnumerable(key){
  var E = isEnum.call(this, key);
  return E || !has(this, key) || !has(AllSymbols, key) || has(this, HIDDEN) && this[HIDDEN][key]
    ? E : true;
};
var $getOwnPropertyDescriptor = function getOwnPropertyDescriptor(it, key){
  var D = getDesc(it = toIObject(it), key);
  if(D && has(AllSymbols, key) && !(has(it, HIDDEN) && it[HIDDEN][key]))D.enumerable = true;
  return D;
};
var $getOwnPropertyNames = function getOwnPropertyNames(it){
  var names  = getNames(toIObject(it))
    , result = []
    , i      = 0
    , key;
  while(names.length > i)if(!has(AllSymbols, key = names[i++]) && key != HIDDEN && key != META)result.push(key);
  return result;
};
var $getOwnPropertySymbols = function getOwnPropertySymbols(it){
  var names  = getNames(toIObject(it))
    , result = []
    , i      = 0
    , key;
  while(names.length > i)if(has(AllSymbols, key = names[i++]))result.push(AllSymbols[key]);
  return result;
};
var $stringify = function stringify(it){
  if(it === undefined || isSymbol(it))return; // IE8 returns string on undefined
  var args = [it]
    , i    = 1
    , replacer, $replacer;
  while(arguments.length > i)args.push(arguments[i++]);
  replacer = args[1];
  if(typeof replacer == 'function')$replacer = replacer;
  if($replacer || !isArray(replacer))replacer = function(key, value){
    if($replacer)value = $replacer.call(this, key, value);
    if(!isSymbol(value))return value;
  };
  args[1] = replacer;
  return _stringify.apply($JSON, args);
};
var BUGGY_JSON = $fails(function(){
  var S = $Symbol();
  // MS Edge converts symbol values to JSON as {}
  // WebKit converts symbol values to JSON as null
  // V8 throws on boxed symbols
  return _stringify([S]) != '[null]' || _stringify({a: S}) != '{}' || _stringify(Object(S)) != '{}';
});

// 19.4.1.1 Symbol([description])
if(!USE_NATIVE){
  $Symbol = function Symbol(){
    if(isSymbol(this))throw TypeError('Symbol is not a constructor');
    return wrap(uid(arguments.length > 0 ? arguments[0] : undefined));
  };
  redefine($Symbol.prototype, 'toString', function toString(){
    return this._k;
  });

  isSymbol = function(it){
    return it instanceof $Symbol;
  };

  $.create     = $create;
  $.isEnum     = $propertyIsEnumerable;
  $.getDesc    = $getOwnPropertyDescriptor;
  $.setDesc    = $defineProperty;
  $.setDescs   = $defineProperties;
  $.getNames   = $names.get = $getOwnPropertyNames;
  $.getSymbols = $getOwnPropertySymbols;

  if(DESCRIPTORS && !require('./_library')){
    redefine(ObjectProto, 'propertyIsEnumerable', $propertyIsEnumerable, true);
  }
}

$export($export.G + $export.W + $export.F * !USE_NATIVE, {Symbol: $Symbol});

// 19.4.2.2 Symbol.hasInstance
// 19.4.2.3 Symbol.isConcatSpreadable
// 19.4.2.4 Symbol.iterator
// 19.4.2.6 Symbol.match
// 19.4.2.8 Symbol.replace
// 19.4.2.9 Symbol.search
// 19.4.2.10 Symbol.species
// 19.4.2.11 Symbol.split
// 19.4.2.12 Symbol.toPrimitive
// 19.4.2.13 Symbol.toStringTag
// 19.4.2.14 Symbol.unscopables
$.each.call((
  'hasInstance,isConcatSpreadable,iterator,match,replace,search,' +
  'species,split,toPrimitive,toStringTag,unscopables'
).split(','), function(it){
  var Wrapper = core.Symbol
    , sym     = wks(it);
  if(!(it in Wrapper))setDesc(Wrapper, it, {value: USE_NATIVE ? sym : wrap(sym)});
});

setter = true;

$export($export.S + $export.F * !USE_NATIVE, 'Symbol', {
  // 19.4.2.1 Symbol.for(key)
  'for': function(key){
    return has(SymbolRegistry, key += '')
      ? SymbolRegistry[key]
      : SymbolRegistry[key] = $Symbol(key);
  },
  // 19.4.2.5 Symbol.keyFor(sym)
  keyFor: function keyFor(key){
    return keyOf(SymbolRegistry, key);
  },
  useSetter: function(){ setter = true; },
  useSimple: function(){ setter = false; }
});

$export($export.S + $export.F * !USE_NATIVE, 'Object', {
  // 19.1.2.2 Object.create(O [, Properties])
  create: $create,
  // 19.1.2.4 Object.defineProperty(O, P, Attributes)
  defineProperty: $defineProperty,
  // 19.1.2.3 Object.defineProperties(O, Properties)
  defineProperties: $defineProperties,
  // 19.1.2.6 Object.getOwnPropertyDescriptor(O, P)
  getOwnPropertyDescriptor: $getOwnPropertyDescriptor,
  // 19.1.2.7 Object.getOwnPropertyNames(O)
  getOwnPropertyNames: $getOwnPropertyNames,
  // 19.1.2.8 Object.getOwnPropertySymbols(O)
  getOwnPropertySymbols: $getOwnPropertySymbols
});

// 24.3.2 JSON.stringify(value [, replacer [, space]])
$JSON && $export($export.S + $export.F * (!USE_NATIVE || BUGGY_JSON), 'JSON', {stringify: $stringify});

// 19.4.3.5 Symbol.prototype[@@toStringTag]
setToStringTag($Symbol, 'Symbol');
// 20.2.1.9 Math[@@toStringTag]
setToStringTag(Math, 'Math', true);
// 24.3.3 JSON[@@toStringTag]
setToStringTag(global.JSON, 'JSON', true);