docs: function WebWorker_on(method,           // @arg MethodNameString
                        methodCallback) { // @arg Function - methodCallback(err:Error, body:Any, param:Object):void
                                          // @ret this
  //{@dev
      $valid($type(method,         "MethodNameString"), WebWorker_on, "method");
      $valid($type(methodCallback, "Function"),         WebWorker_on, "methodCallback");
  //}@dev
  
      this._on[method] = methodCallback;
      return this;
  }