javascript里的继承

js里面继承的方式，

1. 类式继承，通过构造函数的继承

 function extend(subClass, superClass){
     var F = function(){};
     F.prototype = superClass.prototype;
     subClass.prototype = new F();
     subClass.prototype.constructor = subClass;

     subClass.superclass = superClass.prototype; // optional
     if (superClass.prototype.constructor == Object.prototype.constructor){
         superClass.prototype.constructor = superClass;
     }
 }

2. 原型式继承，通过对象的继承

function clone(object){
    function F(){}
    F.prototype = object;
    return new F();
}