function alphabetizeList() {
    var sel = $(listField);
    var selected = sel.val(); // cache selected value, before reordering
    var opts_list = sel.find('option');
    opts_list.sort(function (a, b) {
        return $(a).text() > $(b).text() ? 1 : -1;
    });
    sel.html('').append(opts_list);
    sel.val(selected); // set cached selected value
}

alphabetizeList('#FIELDID');