javascript有参构造函数

<script type="text/javascript">
	function Person(myname,age){
		this.nam = myname;
		this.age = age;
		this.showInfo = function(){
			return ("my name's "+this.nam+",now age " +this.age);
		}
	}

	var person = new Person("shizi",21);
	document.writeln(person.showInfo());
	document.writeln("<pre>"+person.constructor()+"</pre>");
</script>