docs: function EventListener_register(types) { // @arg EventTypeStringArray - ["type", ...]
                                           // @ret this
                                           // @desc register types
  //{@dev
      $valid($type(types, "Array"), EventListener_register, "types");
  //}@dev
  
  //{@dev
      var that = this;
  
      // avoid duplicate
      types.forEach(function(type) {
          if (that._types.indexOf(type) < 0) {
              that._types.push(type);
          }
      });
  //}@dev
      return this;
  }