window . watcher = { _value : null };
 Object . defineProperty ( watcher ,'value',
     {
         set : function ( v ){
             console . log ('o bojemoy!', v );
             this . _value = v ;
         },
         get : function (){
             return this . _value ;
         }
     },
 )

 window . watcher . value = 1 ;
 window . watcher . value = 10 ;
 window . watcher . value = 15 ;