Dependent jquery select lists

gistfile1.js

$(".country_selector").change( function(){
    if ($(".region_selector").length > 0){
      $.getJSON('/countries/'+$(this).val(), function(data) {
        $(".region_selector").html($("<option></option>"));
        $.each(data.country.regions, function(index, region){
          $(".region_selector").
            append($("<option></option>").
            attr("value",region.id).
            text(region.name));        
        });
      });
    }
  });