js寄生组合式继承

function extend(sub,sup){
var F=function(){};
F.prototype=sup.prototype;
var prototype=new F();
//var prototype=Object(sup.prototype);/*上面三句可以用这一句代替,但任意子类对象在原型上的改动都会影响其它子类对象,不合适*/

prototype.constructor=sub;
sub.prototype=prototype;
}
/*父类*/
function Sup(){}
/*子类*/
function Sub(name,age){
sup.call(this,name);
this.age=age;
}
extend(Sub,Sup);