es.symbol.description.js

// `Symbol.prototype.description` getter
// https://tc39.es/ecma262/#sec-symbol.prototype.description
'use strict';
var $ = require('../internals/export');
var DESCRIPTORS = require('../internals/descriptors');
var global = require('../internals/global');
var uncurryThis = require('../internals/function-uncurry-this');
var hasOwn = require('../internals/has-own-property');
var isCallable = require('../internals/is-callable');
var isPrototypeOf = require('../internals/object-is-prototype-of');
var toString = require('../internals/to-string');
var defineBuiltInAccessor = require('../internals/define-built-in-accessor');
var copyConstructorProperties = require('../internals/copy-constructor-properties');

var NativeSymbol = global.Symbol;
var SymbolPrototype = NativeSymbol && NativeSymbol.prototype;

if (DESCRIPTORS && isCallable(NativeSymbol) && (!('description' in SymbolPrototype) ||
  // Safari 12 bug
  NativeSymbol().description !== undefined
)) {
  var EmptyStringDescriptionStore = {};
  // wrap Symbol constructor for correct work with undefined description
  var SymbolWrapper = function Symbol() {
    var description = arguments.length < 1 || arguments[0] === undefined ? undefined : toString(arguments[0]);
    var result = isPrototypeOf(SymbolPrototype, this)
      ? new NativeSymbol(description)
      // in Edge 13, String(Symbol(undefined)) === 'Symbol(undefined)'
      : description === undefined ? NativeSymbol() : NativeSymbol(description);
    if (description === '') EmptyStringDescriptionStore[result] = true;
    return result;
  };

  copyConstructorProperties(SymbolWrapper, NativeSymbol);
  SymbolWrapper.prototype = SymbolPrototype;
  SymbolPrototype.constructor = SymbolWrapper;

  var NATIVE_SYMBOL = String(NativeSymbol('description detection')) === 'Symbol(description detection)';
  var thisSymbolValue = uncurryThis(SymbolPrototype.valueOf);
  var symbolDescriptiveString = uncurryThis(SymbolPrototype.toString);
  var regexp = /^Symbol\((.*)\)[^)]+$/;
  var replace = uncurryThis(''.replace);
  var stringSlice = uncurryThis(''.slice);

  defineBuiltInAccessor(SymbolPrototype, 'description', {
    configurable: true,
    get: function description() {
      var symbol = thisSymbolValue(this);
      if (hasOwn(EmptyStringDescriptionStore, symbol)) return '';
      var string = symbolDescriptiveString(symbol);
      var desc = NATIVE_SYMBOL ? stringSlice(string, 7, -1) : replace(string, regexp, '$1');
      return desc === '' ? undefined : desc;
    }
  });

  $({ global: true, constructor: true, forced: true }, {
    Symbol: SymbolWrapper
  });
}