constrcutor

/**
 * Created by Administrator on 2015/5/11.
 */
var Super = function(){
};
Super.prototype.sayHello = function(){};

var Sub = function(){
    Super.call(this);
};

Sub.prototype = new Super();
Sub.prototype.constructor = Sub;//为什么要指回来？
//因为Sub.constructor变成了Super，
// 构造函数如果需要辨别自己是谁构造出来的，就需要指回来
Sub.prototype.subSayHello = function(){};

var sub = new Sub();

var s = new Super();

sub.constructor === Sub //true
sub.constructor === Super //false

sub.__proto__ instanceof Super //true
sub.__proto__ instanceof Sub //false