JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="mylist">
   <li> item 1</li>
   <li> item 2</li>
</ul>
<div id="Counter"></div>

CSS

#Counter{font-family:square721 bt; background:#222; border-radius:20px; color:#fff; width:20px;}

JavaScript

function updateNotificationCount(){    
    var nCount=$("#mylist li").length; 
        $("#Counter").html(nCount);     
    }

 $(document).ready(function(){
   $.ajax({
        type: "POST",
        url: "/echo/html/",
       data: {html:'<li> item 3</li><li> item 4</li><li> item 8</li><li> item 8</li>'},

        success: function (data) {

              $('#mylist').append(data);
              updateNotificationCount();


        },
        error: function (xhr, ajaxOptions, thrownError) {alert("error");
            alert(xhr.statusText);
            alert(xhr.responseText);
            alert(xhr.status);
            alert(thrownError);
        }

        });
});