Riak - How to get the ID of the current item in a Map function

Question

Using Riak, how can I get the ID of the current item that's being processed in a Javascript map function?

function(v, kd, arg) {
    var element = v.values[0];
    var id = "??"; // How to get the ID of the current item
    return [id];
}

Answer 1

I've discovered how to do it:

function(v, kd, arg) {
    return [v.key];
}

I've found the source on: http://contrib.basho.com/get_keys.html