DataTable - Custom Data source sorting

HTML

<link rel="stylesheet" href="//cdn.datatables.net/1.9.4/css/jquery.dataTables.css">
<script src="//cdn.datatables.net/1.9.4/js/jquery.dataTables.js"></script>
<body>
    <table id="example">
        <thead>
            <tr>
                <th>header 1</th>
                <th>header 2</th>
            </tr>
        </thead>
        <tbody>
            <tr>
                <td>
                    <select size="1" id="row-1-office" name="row-1-office">
                        <option value="Edinburgh" selected="selected"> Edinburgh </option>
                        <option value="London">London </option>
                        <option value="New York">New York </option>
                        <option value="San Francisco">San Francisco </option>
                        <option value="Tokyo"> Tokyo </option>
                    </select>
                </td>
                <td>
                    <select size="1" id="row-1-office" name="row-1-office">
                        <option value="1Edinburgh" selected="selected">1Edinburgh</option>
                        <option value="1London">1London</option>
                        <option value="1New York">1New York</option>
                        <option value="1San Francisco">1San Francisco</option>
                        <option value="1Tokyo">1Tokyo</option>
                    </select>
                </td>
            </tr>
            <tr>
                <td><select size="1" id="row-1-office" name="row-1-office">
                    <option value="Edinburgh">
                        Edinburgh
                    </option>

                    <option value="London"  selected="selected">
                        London
                    </option>

                    <option value="New York">
                        New York
                    </option>

                    <option value="San Francisco">
                        San Francisco
                    </option>

                    <option...

JavaScript

$.fn.dataTableExt.afnSortData['dom-text'] = function (oSettings, iColumn) {

    var aData = [];
    $('td:eq(' + iColumn + ') input',   oSettings.oApi._fnGetTrNodes(oSettings)).each(function () {
        aData.push(this.value);
    });
    return aData;
};

$.fn.dataTableExt.afnSortData['dom-select'] = function (oSettings, iColumn) {
    var aData = [];
    $('td:eq(' + iColumn + ') select', oSettings.oApi._fnGetTrNodes(oSettings)).each(function () {
        aData.push(this.value);
    });
    return aData;
};
/*$.fn.dataTable.ext.order['dom-text'] = function  ( settings, col )
{
    return this.api().column( col, {order:'index'} ).nodes().map( function ( td, i ) {
        return $('input', td).val();
    } );
}
*/
var table = $('#example').dataTable({
    aoColumns: [
    {
        sSortDataType: 'dom-select'
    },
    {
        sSortDataType: 'dom-select'
    }]
});