code: function parseArguments(url, data, success, dataType) {
      if ($.isFunction(data)) dataType = success, success = data, data = undefined
      if (!$.isFunction(success)) dataType = success, success = undefined
      return {
        url: url
      , data: data
      , success: success
      , dataType: dataType
      }
    }
docs: handle optional data/success arguments