jquery ajax动态追加select选择框

$(document).ready(function(){
        $("#volumeIDdetach").change(function(){
            if(this.selectedIndex==0)return;
            $("#instanceIDdetach").empty();
            $("#volumeIDdetach").attr("disabled",true);
            $.ajax({
                type:"POST", 
                url:"/usmccm/vodaplex/volume/showAllvolumesAction.do?isAjax=true",//处理请求的action方法 
                data:"volumeID="+$("#volumeIDdetach option:selected").val()+"&ajaxvolumeID="+$("#volumeIDdetach option:selected").val(),//传递的参数 
                success:function(html){
                $("#volumeIDdetach").attr("disabled",false);
                $("#onLoadInstance").attr("display","none");
                var htmlarr = html.split("//@");
                for(var i = 0;i < htmlarr.length - 1;i++)
                {
                    $("#instanceIDdetach").append("<option value="+htmlarr[i]+" >"+htmlarr[i]+"</option>");   
                }
                } 
            }); 
        });
});