How to change select list from another using AJAX in Joomla

Question

I have a list of countries and a list of cities for each country. I set both as drop-down list.

My problem is how can I change the cities listed when the selected co

Answer 1

A note appart, you're using the deprecated JRequest::getInt(); where you should be using

$input = JFactory::getApplication()->input;
$country_id = $input->getInt('country_id', 0);

In order to change the second select, you must trigger the update of the second select:

$(".country").change(function(){
    // your ajax call from your code

    // on success, you need to trigger the second select by using
    $( ".city_id" ).val(your_value_from_ajax_response).trigger( "liszt:updated" );

});