javascript中基于原型法直接实现继承中的一个陷阱和解决

Object.prototype.extend = function (aClass) {   
    this.prototype = new aClass   
}   
....

function Base(){ 
    this.x = 100
    this.y = 10 
    this.area = function(){
        return this.x * this.y
    }
}

function Child(){
    this.x = 10
    this.area = function(){
        return this.__proto__.area() + 100000
    }
}

Child.extend(Base)

js> c = new Child()
[object Object]
js> c.area()
101000.0

function ChildB(){    
    this.x = 10;  
    this.oldArea=this.area; 
    this.area = function(){
        return this.oldArea() + 100000    
        }
}
ChildB.extend(Base)

js> b = new ChildB()
[object Object]
js> b.area()
100100.0

function Child() {
    this.x = 10
    this.area = function () {
        return this.__proto__.area.apply(this) + 100000
    }
}