onmessage property
      
      EventHandlerNonNull<Event> ?
      get
      onmessage
      
    
    
    
Implementation
EventHandlerNonNull? get onmessage => js_util.getProperty(this, 'onmessage');
      
      set
      onmessage
      (EventHandlerNonNull<Event> ? newValue) 
      
    
    
    
Implementation
set onmessage(EventHandlerNonNull? newValue) {
  js_util.setProperty(this, 'onmessage', newValue);
}