select 改变时,执行ajax操作

<select  class="select01 ss1"  name="pp">
  <option class="pid" value ="0">ALL</option>
  <?php foreach($pp as $k=>$vo): ?>
    <option  value ="{$vo['cid']}">{$vo['name']}</option>
  <?php endforeach; ?>
</select>

$(".ss1").on('change',function(){
    // var pid = $(".select01 option[selected='selected']").val();
    var pid = $(".select01 option:selected").val();
    // var pay_num = $("#pay_num li[class='on']").attr("rel");
    // console.log(pid);
    $.ajax({
        type:'get',
        url:'__URL__/ajax_fan2.html',
        data:{id:pid},
        dataType:'json',
        success:function(res){
            if(res.result==1){
               // alert(res.msg);
                // alert(res.msg.length);
                var html='';

                $(".ss2").html('');
                html+='<option value ="0">size</option>';
                for(var i=0;i<res.msg.length;i++){
                  html+='<option value ="'+res.msg[i].cid+'">'+res.msg[i].name+'</option>';

                }
                $(".ss2").append(html);

               // location.href="__APP__/member/index.html"
            }else{
                // alert(res.msg);
            }

        }
    })
     
  })