javascript get set读取器

     class Person{

         constructor(name, id){

             let _name = name, _id = id;

             Object.defineProperties(this, {

                 name:{
                     //每次获取this.name的时候都会调用get方法
                     get:()=>{return _name;},
                     //每次修改this.name的时候都会调用set方法
                     set:(v)=>{_name = v; document.write(v);}
                 },

                 id:{
                     get:()=>{return _id;},
                     set:(v)=>{_id = v; document.write(v);}
                 }

             });

         }

     }
     //test
     let p = new Person("w_1");
     console.log(p);
     p.name = "w_2";//w_2