Delete data of User details from-Java scrpt

function deleteData()
{

var userid =document.getElementById('cboUser').value;
if(userid!='')
{
var url ="user_db.php?id=deleteData";
url+="&userid="+userid;


var htmlhttp_obj  = $.ajax({url:url,async:false});
alert(htmlhttp_obj.responseText);

window.location.href = 'users.php';

}
else
alert("Please select a User to DELETE!");


}