[Rails][JQuery]いつも忘れるDynamic select options

結構な頻度で書く依存型セレクトボックス。毎回自力で書いてるような気がするのでログしておく。

 <div class="field">
    <%= form.label :region %>
    <%= form.select :region, options_for_select([
      'us-west-2',
      'us-west-1',
      'us-east-2',
      'us-east-1',
      'ap-south-1',
      'ap-northeast-2',
      'ap-southeast-1',
      'ap-southeast-2',
      'ap-northeast-1',
      'ca-central-1',
      'cn-north-1',
      'eu-central-1',
      'eu-west-1',
      'eu-west-2',
      'eu-west-3',
      'sa-east-1'
    ]), {include_blank: true}, required: true %>
  </div>

  <div class="field">
    <%= form.label :availability_zone %>
    <%= form.select :availability_zone, {}, required: true %>
  </div>

<script>
 $("#storage_region").change(function(){
    var region = $(this).val();
    var $saz = $('#storage_availability_zone');
    $.get("/api/v1/aws_availability_zones?region="+region, function(zones){
      $saz.empty();
      zones.forEach(function(zone){
        $('<option>').val(zone).text(zone).appendTo($saz)
      })
    });
  })
</script>