Jquery datatables format numbers

$('#table-dg').dataTable({
    "columns": columnNames,
    "columnDefs": [
        {
            "render": function (data, type, row) {
                 return commaSeparateNumber(data);
            },
            "targets": [1,2]
        },
    ]
});

function commaSeparateNumber(val) {
    while (/(\d+)(\d{3})/.test(val.toString())) {
        val = val.toString().replace(/(\d+)(\d{3})/, '$1' + ',' + '$2');
    }

    return val;
}

As mentioned in my comment you have to do something like this

Inside Datatable initialization :

 "aoColumnDefs": [ {
      "aTargets": [ 2 ],
    "mRender": function (data, type, full) {
     var formmatedvalue=data.replace(//regex expression)
      return formmatedvalue;
    }
}]

There is actually an even easier way to do this, also found on the datatables documentation:

        "columns": [
            { "data": "ReceiptQuantity", render: $.fn.dataTable.render.number(',', '.', 2, '') },
            { "data": "ReceiptPrice", render: $.fn.dataTable.render.number(',', '.', 2, '') },
            { "data": "LineTotal", render: $.fn.dataTable.render.number(',', '.', 2, '') }
        ],