core-js/modules/es6.symbol.js

Standard library

'use strict';
// ECMAScript 6 symbols shim
var $              = require('./$')
  , global         = require('./$.global')
  , has            = require('./$.has')
  , SUPPORT_DESC   = require('./$.support-desc')
  , $def           = require('./$.def')
  , $redef         = require('./$.redef')
  , shared         = require('./$.shared')
  , setTag         = require('./$.tag')
  , uid            = require('./$.uid')
  , wks            = require('./$.wks')
  , keyOf          = require('./$.keyof')
  , $names         = require('./$.get-names')
  , enumKeys       = require('./$.enum-keys')
  , isObject       = require('./$.is-object')
  , anObject       = require('./$.an-object')
  , toIObject      = require('./$.to-iobject')
  , createDesc     = require('./$.property-desc')
  , getDesc        = $.getDesc
  , setDesc        = $.setDesc
  , _create        = $.create
  , getNames       = $names.get
  , $Symbol        = global.Symbol
  , setter         = false
  , HIDDEN         = wks('_hidden')
  , isEnum         = $.isEnum
  , SymbolRegistry = shared('symbol-registry')
  , AllSymbols     = shared('symbols')
  , useNative      = typeof $Symbol == 'function'
  , ObjectProto    = Object.prototype;

var setSymbolDesc = SUPPORT_DESC ? function(){ // fallback for old Android
  try {
    return _create(setDesc({}, HIDDEN, {
      get: function(){
        return setDesc(this, HIDDEN, {value: false})[HIDDEN];
      }
    }))[HIDDEN] || setDesc;
  } catch(e){
    return 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;
  SUPPORT_DESC && 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 $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)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;
};

// 19.4.1.1 Symbol([description])
if(!useNative){
  $Symbol = function Symbol(){
    if(this instanceof $Symbol)throw TypeError('Symbol is not a constructor');
    return wrap(uid(arguments[0]));
  };
  $redef($Symbol.prototype, 'toString', function toString(){
    return this._k;
  });

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

  if(SUPPORT_DESC && !require('./$.library')){
    $redef(ObjectProto, 'propertyIsEnumerable', $propertyIsEnumerable, true);
  }
}

// MS Edge converts symbol values to JSON as {}
// WebKit converts symbol values in objects to JSON as null
if(!useNative || require('./$.fails')(function(){
  return JSON.stringify([{a: $Symbol()}, [$Symbol()]]) != '[{},[null]]';
}))$redef($Symbol.prototype, 'toJSON', function toJSON(){
  if(useNative && isObject(this))return this;
});

var symbolStatics = {
  // 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; }
};
// 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 sym = wks(it);
    symbolStatics[it] = useNative ? sym : wrap(sym);
  }
);

setter = true;

$def($def.G + $def.W, {Symbol: $Symbol});

$def($def.S, 'Symbol', symbolStatics);

$def($def.S + $def.F * !useNative, '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
});

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