core-js/internals/symbol-is-well-known.js

'use strict';
var shared = require('../internals/shared');
var getBuiltIn = require('../internals/get-built-in');
var uncurryThis = require('../internals/function-uncurry-this');
var isSymbol = require('../internals/is-symbol');
var wellKnownSymbol = require('../internals/well-known-symbol');

var Symbol = getBuiltIn('Symbol');
var $isWellKnownSymbol = Symbol.isWellKnownSymbol;
var getOwnPropertyNames = getBuiltIn('Object', 'getOwnPropertyNames');
var thisSymbolValue = uncurryThis(Symbol.prototype.valueOf);
var WellKnownSymbolsStore = shared('wks');

for (var i = 0, symbolKeys = getOwnPropertyNames(Symbol), symbolKeysLength = symbolKeys.length; i < symbolKeysLength; i++) {
  // some old engines throws on access to some keys like `arguments` or `caller`
  try {
    var symbolKey = symbolKeys[i];
    if (isSymbol(Symbol[symbolKey])) wellKnownSymbol(symbolKey);
  } catch (error) { /* empty */ }
}

// `Symbol.isWellKnownSymbol` method
// https://tc39.es/proposal-symbol-predicates/#sec-symbol-iswellknownsymbol
// We should patch it for newly added well-known symbols. If it's not required, this module just will not be injected
module.exports = function isWellKnownSymbol(value) {
  if ($isWellKnownSymbol && $isWellKnownSymbol(value)) return true;
  try {
    var symbol = thisSymbolValue(value);
    for (var j = 0, keys = getOwnPropertyNames(WellKnownSymbolsStore), keysLength = keys.length; j < keysLength; j++) {
      // eslint-disable-next-line eqeqeq -- polyfilled symbols case
      if (WellKnownSymbolsStore[keys[j]] == symbol) return true;
    }
  } catch (error) { /* empty */ }
  return false;
};