biobulkbende.org/node_modules/es6-symbol/lib/private/setup/symbol-registry.js

"use strict";

var d              = require("d")
  , validateSymbol = require("../../../validate-symbol");

var registry = Object.create(null);

module.exports = function (SymbolPolyfill) {
	return Object.defineProperties(SymbolPolyfill, {
		for: d(function (key) {
			if (registry[key]) return registry[key];
			return (registry[key] = SymbolPolyfill(String(key)));
		}),
		keyFor: d(function (symbol) {
			var key;
			validateSymbol(symbol);
			for (key in registry) {
				if (registry[key] === symbol) return key;
			}
			return undefined;
		})
	});
};