function person(name,age)
            {
                this.name=name;
                this.age=age;
                this.showInheritance=function()
                {
                    document.write(this.name+" "+this.age);
                }
            }
            function dog(name,age)
            {
                this.x=person;
                this.x(name.age);
            }
            var dog1=new dog("bage",3);
            dog1.showInheritance();

            function dog(name,age) {
                this.x=person;
                this.x(name, age); //刚才标注错了，你这里有低级错误，逗号写成点号了
            }