function Parent(name){

    this.name = name;

    this.sayName  = function(){

       console.log(this.name);

   }

}

function Son(name,password){

  this.method = Parent;

  this.method(name);

  this.show = function(){

       console.log(this.name+' : '+this.password)

   }

  delete this.method;

}

var son1 = new Son('zhangsan','123456');

son1.show();