Getting user id from server

I am getting user's id to add/update them in a list.

If I try to get the users who are already added(added in SharePoint group) in the sharepoint site, i am able to get the id by below code.

var ProdOwnercount = (ProductOwnerArray.length-1);
var ProductOwner = new Array();

for(j=1;j<=ProdOwnercount;j++)
{
var ProdOwnerdata = ProductOwnerArray[j];
var lines = ProdOwnerdata.split("<Value xsi:type=\"xsd:string\">");
var len = lines.length;
var id1 = lines[1];
var id = id1.split("<");
ProductOwner[j]=id[0];
}

If the users are not added or accessed the sharepoint site, how to get their id from user profile?

i want to achieve this using javascript/jquery.

Thanks,

Sriram