Update select option based in ajax request

prototype-update-select-option.md

PHP

    public function stateSearchAction()
    {
        $country = $this->getRequest()->getParam('code');
        $collection = Mage::getModel('directory/region')->getCollection()
            ->addFieldToFilter('country_id', $country)->getData();
        $this->getResponse()->clearHeaders()->setHeader('Content-type', 'application/json');
        $this->getResponse()->setBody(Zend_Json::encode($collection));
    }

JS

document.observe('dom:loaded', function () {
    $('country').observe('change', function () {
        var country = this.value;
        new Ajax.Request('/perfil-fornecedor/index/stateSearch', {
            method: 'get',
            parameters: {code: country},
            onSuccess: function(response) {
                var states = response.responseJSON;
                $('state').select('option').invoke('remove');

                if( states.length > 0) {
                    for(var i = 0; i <= states.length;i++ ) {
                        console.log(states[i].code, states[i].default_name);
                        $('state').insert(new Element('option', {value: states[i].code}).update(states[i].default_name));
                    }
                }

            }
        });
    })
});