js继承——扩展Object方式实现继承

function Parent(name,sex){
    this.name  = name;
    this.sex = sex;
    this.sayName = function(){
        console.log(this.name+' : '+this.sex);
    }
}

Object.prototype.method = function(obj){
         for (var attr in obj){
            this[attr] = obj[attr];
        }
}

function Son(age){
    this.age = age;
    this.show = function(){
       console.log(this.name+' : '+this.sex+' : '+this.age);
    }      
}

var p1 = new Parent('zhangsan','男');
var p2 = new Son(23);
p2.method(p1);

p2.show();

因为给原型链的的顶端添加方法，所以所有的对象都会添加此属性和方法