js构造继承的缺点

function Star(name,age){

this.name=name

        this.age=age

        this.sayName=function(){

            console.log(this.name)

        }

    }

Star.prototype.sing=function(){

        alert(this.name)

    }

var ldh=new Star('刘德华',28)

var zxy=new Star('张学友',29)