Javascript访问器属性实例分析

varbook={
   _year:2004,
   edition:1
};
Object.defineProperty(book,"year",{
   get:function(){
       returnthis._year;
   },
   set:function(newValue){
       if(newValue>2004){
           this._year+=newValue;
           this.edition+=newValue-2004;
       }
   }
});
book.year=2006;
console.log(book.edition);