javascript - ajax asynchronously requests data, ios screen flashes

When making a chat page, when ajax requests data asynchronously, regardless of whether there is data returned, ios will flash, but android will not flash. What is going on and how to solve it

<code>$(document).ready(function(){
        $('.loading_box').attr('style','display:none');
        ajaxform();
        window.setInterval("ajaxform()",3000); 

    });
    

function ajaxform(){
    var id=$(".main_box ul li:last-child").find('.delete_btn').attr('field');//alert(id);
    $.post(
        "{:U('App/Friends/ajaxform')}",
        {"openid":openid,"id":id},
        function(data){
          if (data) {
            var str = "";console.log(data);
            $.each(data, function(index, array) {
              if(array['openid']==openid){
                if(array['type']==0){
                  //普通文字或图片
                  str='<li class="chart-right"><div class="chart_text_box"><div class="jieshao"><p>'+array['uname']+'</p><p>'+array['time']+'</p></div><div class="chart_text_qipao_right"><p>'+array['content']+'</p></div><div class="operation_box"><div class="delete_btn" field="'+array['id']+'">删除</div></div></div><div class="persion_img_right"><img src="'+array['headimgurl']+'"><font><img src="{$tpl}App/Friends/Public/img/vipv'+array['classid']+'l.png"></font></div></li>';
                }else{
                  //我的霸屏
                  str='<li class="chart-right"><div class="chart_text_box"><div class="jieshao"><p>'+array['uname']+'</p><p>'+array['time']+'</p></div><div class="chart_text_qipao_right"><p><i class="money_text">重金霸屏'+arr[array['type']]+'秒</i>'+array['content'];
                  if(array['img']!=""){
                    str+='<font class="chart_img"><img src="'+array['img']+'"></font>';
                  }
                  str+='</p></div><div class="operation_box"><div class="delete_btn" field="'+array['id']+'">删除</div></div></div> <div class="persion_img_right"><img src="'+array['headimgurl']+'"><font><img src="{$tpl}App/Friends/Public/img/vipv'+array['classid']+'l.png"></font></div> </li>';
                }  
              }else{
                if(array['type']==0){
                  //普通文字或图片
                  str = ' <li class="chart-left"><div class="persion_img_left"><img src="'+array['headimgurl']+'"><font><img src="{$tpl}App/Friends/Public/img/vipv'+array['classid']+'l.png"></font></div> <div class="chart_text_box"><div class="jieshao"><p>'+array['uname']+'</p><p>'+array['time']+'</p></div><div class="chart_text_qipao_left"><span class="sanjiao_left"></span><p>'+array["content"]+'</p></div>';
                  if(isadmin){
                    str+='<div class="operation_box"><div class="delete_btn" field="'+array['id']+'">删除</div> <div class="blacklist" field="'+array['openid']+'">拉黑</div></div>';
                  }
                  str+='</div> </li>';
                }else{
                  //他人霸屏
                  str='<li class="chart-left "><div class="persion_img_left"><img src="'+array['headimgurl']+'"><font><img src="{$tpl}App/Friends/Public/img/vipv'+array['classid']+'l.png"></font></div> <div class="chart_text_box"><div class="jieshao"><p>'+array['uname']+'</p><p>'+array['time']+'</p></div><div class="chart_text_qipao_left"><span class="sanjiao_left"></span><p><i class="money_text">重金霸屏'+arr[array['type']]+'秒</i>'+array['content'];
                  if(array['img']!=""){
                    str+='<font class="chart_img"><img src="'+array['img']+'"></font>';
                  }
                  str+='</p></div>';
                  if(isadmin){
                    str+='<div class="operation_box"><div class="delete_btn" field="'+array['id']+'">删除</div> <div class="blacklist" field="'+array['openid']+'">拉黑</div></div>';
                  }
                  str+='</div> </li>';
                }
              }
              $(".main_box ul").append(str);
              $('.main_box').scrollTop( $('.main_box')[0].scrollHeight );
            });
          }
                     
        }
    );
}</code>

Reply content:

When making a chat page, when ajax requests data asynchronously, regardless of whether there is data returned, ios will flash, but android will not flash. What is going on and how to solve it

<code>$(document).ready(function(){
        $('.loading_box').attr('style','display:none');
        ajaxform();
        window.setInterval("ajaxform()",3000); 

    });
    

function ajaxform(){
    var id=$(".main_box ul li:last-child").find('.delete_btn').attr('field');//alert(id);
    $.post(
        "{:U('App/Friends/ajaxform')}",
        {"openid":openid,"id":id},
        function(data){
          if (data) {
            var str = "";console.log(data);
            $.each(data, function(index, array) {
              if(array['openid']==openid){
                if(array['type']==0){
                  //普通文字或图片
                  str='<li class="chart-right"><div class="chart_text_box"><div class="jieshao"><p>'+array['uname']+'</p><p>'+array['time']+'</p></div><div class="chart_text_qipao_right"><p>'+array['content']+'</p></div><div class="operation_box"><div class="delete_btn" field="'+array['id']+'">删除</div></div></div><div class="persion_img_right"><img src="'+array['headimgurl']+'"><font><img src="{$tpl}App/Friends/Public/img/vipv'+array['classid']+'l.png"></font></div></li>';
                }else{
                  //我的霸屏
                  str='<li class="chart-right"><div class="chart_text_box"><div class="jieshao"><p>'+array['uname']+'</p><p>'+array['time']+'</p></div><div class="chart_text_qipao_right"><p><i class="money_text">重金霸屏'+arr[array['type']]+'秒</i>'+array['content'];
                  if(array['img']!=""){
                    str+='<font class="chart_img"><img src="'+array['img']+'"></font>';
                  }
                  str+='</p></div><div class="operation_box"><div class="delete_btn" field="'+array['id']+'">删除</div></div></div> <div class="persion_img_right"><img src="'+array['headimgurl']+'"><font><img src="{$tpl}App/Friends/Public/img/vipv'+array['classid']+'l.png"></font></div> </li>';
                }  
              }else{
                if(array['type']==0){
                  //普通文字或图片
                  str = ' <li class="chart-left"><div class="persion_img_left"><img src="'+array['headimgurl']+'"><font><img src="{$tpl}App/Friends/Public/img/vipv'+array['classid']+'l.png"></font></div> <div class="chart_text_box"><div class="jieshao"><p>'+array['uname']+'</p><p>'+array['time']+'</p></div><div class="chart_text_qipao_left"><span class="sanjiao_left"></span><p>'+array["content"]+'</p></div>';
                  if(isadmin){
                    str+='<div class="operation_box"><div class="delete_btn" field="'+array['id']+'">删除</div> <div class="blacklist" field="'+array['openid']+'">拉黑</div></div>';
                  }
                  str+='</div> </li>';
                }else{
                  //他人霸屏
                  str='<li class="chart-left "><div class="persion_img_left"><img src="'+array['headimgurl']+'"><font><img src="{$tpl}App/Friends/Public/img/vipv'+array['classid']+'l.png"></font></div> <div class="chart_text_box"><div class="jieshao"><p>'+array['uname']+'</p><p>'+array['time']+'</p></div><div class="chart_text_qipao_left"><span class="sanjiao_left"></span><p><i class="money_text">重金霸屏'+arr[array['type']]+'秒</i>'+array['content'];
                  if(array['img']!=""){
                    str+='<font class="chart_img"><img src="'+array['img']+'"></font>';
                  }
                  str+='</p></div>';
                  if(isadmin){
                    str+='<div class="operation_box"><div class="delete_btn" field="'+array['id']+'">删除</div> <div class="blacklist" field="'+array['openid']+'">拉黑</div></div>';
                  }
                  str+='</div> </li>';
                }
              }
              $(".main_box ul").append(str);
              $('.main_box').scrollTop( $('.main_box')[0].scrollHeight );
            });
          }
                     
        }
    );
}</code>

Flashing means the page has been refreshed, check if there is code to re-render the page.