如何从 jquery 中的数据属性获取 json 解码值

Question

I am working with jquery and right now i am passing "Php array with json encode" in "data attribute" and right now i am trying to get this (json encode) value in jquery, But right now i am getting "new" (after update/new) value instead of existing,How can i do this? Here is my current code

 echo '<td class=try contenteditable="true" data-id="'.$id.'" data-txt="'.json_encode($col).'">'; //$col is array



   <script>
        $("td").keypress(function(e){
            var id = $(this).attr("data-id")
            var newtxt = $(this).attr("data-txt")
             var oldtext = $(this).text();
                 if(e.which == 13) {
                alert('oldtext is '+oldtext);   
            }
     });
    </script>