document.write('
解析:
function a(name,age){
this.age = age ? age : 30;
this.name = name ? name : \' 小明 \'
this.say = function(){
alert(this.name + \' 今年 \' + this.age + \' 岁了! \');
}
}
function b){}
B.prototype = new a();
var c = new b();
c.say();
');