javascript - Error: Undefined data -

i have function fetch new ads in every 10 seconds, im getting error

function getnewads(){     var newer ;     // fetches old value 'data-value' attribute     var old_val = $("#new_data").data('value');     $.ajax({         type: "post",         url: "users/process.php",         data:{             getnewads: "getnewads"         },         cache: false ,         datatype: 'json',         async: false     }).success(function(dat){         if(dat.status == 'success'){             $("#new_data").empty();             for(i = 0;i < dat.counts; i++){                 newer = dat.counts + old_val; alert(old_val); /// problem att old_val alerts object object.                 if(newer > 0){                     $("#new_data").html('<div class="added_ad">'+ newer +' new ads </div>');                     // set 'data-value' attribute #new_data element                     $("#new_data").data('value',newer);                     $("#new_data").show();                 }else{$("#new_data").hide();$("#new_data").data('value',0);}             }         }     }); } 

and html div

 <div id="new_data" class="new_data">  </div> 

i have tested works old_val alerting object object doing wrong ? thanks

if alert old_val shows object object

if alert old_val.val() shows undefined old_val

use .attr() instead of .data()

there known issues incompatible browsers on .data()

change code to

var old_val = $("#new_data").attr('data-value');    

to val object.

notice: .attr() , set, if u want set val obj use

$("#new_data").attr('data-value',newvalue);