OOP in java script

<html>
<body>
http://www.w3schools.com/jsref/jsref_prototype_math.asp


http://javascriptweblog.wordpress.com/2010/06/07/understanding-javascript-prototypes/
<script type="text/javascript">

function employee(name,jobtitle,born)
{
this.name=name;
this.jobtitle=jobtitle;
this.born=born;
}
var fred=new employee("Fred Flintstone","Caveman",1970);

employee.prototype.salary= x();
function x(){return 20000;};
employee.prototype.salarie = function (){return 500;};
document.write(fred.salarie());


</script>