var id = 0;
module.exports = function(key){
  return 'Symbol('.concat(key === undefined ? '' : key, ')_', (++id + Math.random()).toString(36));
};
var id = 0
  , px = Math.random();
module.exports = function(key){
  return 'Symbol('.concat(key === undefined ? '' : key, ')_', (++id + px).toString(36));
};
use one random postfix for all symbols