用反射机制和prototype实现继承

<script type="text/javascript">
function People(){
this.name='chenmin';
this.sex='girl';
this.age=22;
this.speak=function(){
alert('qzuishuai')
}
}
People.prototype.skill='walk';
function Woman(){
}
for(var arr in People.prototype){
Woman.prototype[arr]=People.prototype[arr];
} //通过for in迭代 反射 一一对应的进行赋值 ；
//从而实现让Woman继承People原型上的属性方法；
Woman.prototype.wb='kawayi';
var nvren=new Woman();
alert(nvren.name);//undefined
alert(nvren.skill);//walk
alert(nvren.wb);//kawayi
</script>