function update_dropdowns(el) {

    new Ajax.Request(webroot + '/lodging/update_dropdowns/' + el.id + '/' + encodeURIComponent(el.value), {

        method: 'get',
        onComplete: function (transport) {

            var json = transport.responseText.evalJSON();

            if (json.cities) {
                $('citySelect').innerHTML = json.cities;
            }

            if (json.lodging) {
                $('lodgingSelect').innerHTML = json.lodging;
            }

        }
    });
}