returnValue property
      
      String
      get
      returnValue
      
    
    
The returnValue property of the HTMLDialogElement interface gets
or sets the return value for the dialog, usually to indicate which
button the user pressed to close it.
Implementation
external String get returnValue;
      
      set
      returnValue
      (String value) 
      
    
    
    
Implementation
external set returnValue(String value);