Javascript for Splitting the Date field

Hi all,

I need to split date which is in the format "7/12/2013" and get output as 2013-12-07.

I used the below code which works perfectly fine on JS editor but the Pentaho output I get "NAN" in few places like 2013-NaN-12 or 2013-nan-nan and such

//var Opt_In_Date = "7/12/2013";
var datestring = Opt_In_Date.split("/");
var dt1 = datestring[0];
var mon1 = datestring[1];
var yr1 = datestring[2];
if(dt1<10){dt1 = '0'+dt1};
if(mon1<10){mon1 = '0'+mon1};
var DATE_OF_ACTIVITY1 = yr1+ '-'+ mon1 + '-' +dt1;
//document.write(DATE_OF_ACTIVITY1);


Appreciate any help!!!

Thanks!!