Friend.prototype.constructor = Friend
原先Friend.prototype.constructor指向的是Person
但是感觉并没有什么用

有没有弹出的结果都一样，感觉都很好完成了继承

function Person(name,age){ this.name = name; this.age = age; if(typeof this.sayName != 'function'){ Person.prototype.sayName = function(){ alert(this.name); } } } var per1 = new Person('zhang',23); var per2 = new Person('wagn',23); function Friend(name,age,sex){ Person.call(this,name,age); this.sex = sex; } Friend.prototype = new Person(); Friend.prototype.constructor = Friend; //不斧正时，constructor指向Person Friend.prototype.saySex=function(){ alert(this.sex); } var fri1 = new Friend('wang','11','nan'); var fri2 = new Friend('li','55','nv'); alert(Person.prototype.constructor);