有关原型链的问题

Question

function Shape(){    this.name='Shape';    this.toString=function(){        return this.name;    };}function TwoDShape(){    this.name='2D shape';}function Triangle(side,height){    this.name='Triangle';    this.side=side;    this.height=height;    this.getArea=function(){        return this.side*this.height/2;    };}TwoDShape.prototype=new Shape();Triangle.prototype=new TwoDShape();var my=new Triangle(5,10);my.getArea();//25my.toString();//"Triangle"1.my.toString()被调用时，JavaScript引擎执行路径是怎样的？