prototypeを知る

<script type="text/javascript">
	function Person(name,sex,birthday)  
	{  
	  this.name =name;  
	  this.sex = sex;  
	  this.birthday = birthday;  
	}  
	  
	Person.prototype={  
	  sayHi:function(){  
	    alert("Hi ! I am "+this.name);  
	  },  
	  getNameAndSex:function(){  
		alert(this.name+"_"+this.sex);  
	  }
	}  
	var person1 = new Person('mtea','boy','2011-02-03');  
	var person2 = new Person('xiaotea','boy','2011-02-04');  
	person1.sayHi();  
	person2.getNameAndSex(); 
</script>