jquery获取值，ios获取不到，而android可以

<script type="text/javascript">
var pageurl="{:U('App/Friends/page')}";
var tpl="{$tpl}App/Friends/Public/";
var headimgurl="{$person['headimgurl']}";
var openid="{$person['openid']}";
var uname="{$person['uname']}";
var classid="{$person['classid']}";
var isadmin="{$person['isadmin']}";
var isblack="{$person['isblack']}";
var arr=[0,10,20,30,60];
var contenturl="{:U('App/Friends/getcontent')}";
$(document).ready(function(){
        $('.loading_box').attr('style','display:none');
        ajaxform();
        setInterval("ajaxform()",3000); 
    });
</script>
function ajaxform(){
var id=$(".main_box ul li:last-child").find('.delete_btn').attr('field');alert(id);alert(isadmin);
$.ajax({
    type:'POST',
    url:"{:U('App/Friends/ajaxform')}",
    data:{"openid":openid,"id":id},
    dataType:"json",
    global:false,
    success:function(data){
     
      $.each(data[1],function(e,a){
        isblack=a;
      });      
    }
});

}