Concatenate two field in one in Dynamics crm 2011

In my form I have a date field that gets the current date in yyyy/mm/dd format and a field that auto-generates a number.

I want to populate another field in the following format:

yyyy-mm-dd-autogenreatenumber.

Where the year and month and date are the current dates of the form.

Currently I have this code:

function number()

{

var dateFieldValue = Xrm.Page.getAttribute("date field name").getValue();

var autonumberFieldValue = Xrm.Page.getAttribute("autonum field name").getValue();

var result = dateFieldValue+ "-"+ autonumberFieldValue;

Xrm.Page.getAttribute("the other field name").setValue(result);

}

What I get is the complete date format like Friday July 26th 2013-autonum, whereas I want something like this 2013-07-26-autonum.