我不知道我这说法你明不明白？哈哈，比如以下代码：
<script language="javascript">
function Car()
{
this.name = "桑塔纳";
this.money = 1000000;
}
Car.prototype.color = "红色";
Car.prototype = {getName:function(){return this.name;},getMoney:function(){return this.money;}};
var car = new Car();
alert(car.color);
alert(car.getName());
alert(car.getMoney());
</script>

第一个alert语句打印是：undefined