SOURCE

var book = {};

Object.defineProperties(book, {
  _year : {
    writable : true,
    value : 2004
  },
  edition : {
    writable : true,
    value : 1
  },
  year : {
    get : function(){
      return this._year;
    },
    set : function(newValue){
      if (newValue > 2004)
      {
        this._year = newValue;
        this.edition += newValue - 2004;
      }
    }
  }
});

book.year = 2006;
alert(book.edition);