如何感觉delete this.newMethod;加不加无所谓

怎么感觉delete this.newMethod;加不加无所谓？
function classA(){
this.name="Michael"
this.say=function(){alert(this.name)}
}

function classZ(){
this.sayBye=function (){
alert(886)
}
}

function classB(){
this.newMethod=classA;
this.newMethod();

//delete this.newMethod;

this.newMethod=classZ;
this.newMethod();
//delete this.newMethod;
this.name='jackson';
this.sayName=function (){alert(this.name)}
}


b=new classB
a=new classA
z=new classZ
b.sayName();
a.say();

不加delete this.newMethod超类的属性也没被覆盖啊？

[解决办法]