JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="relatedelements">
   
   <li style="display:none;" class="1">anything</li>
   <li style="display:none;" class="2">anything</li>
   <li style="display:none;" class="3">anything</li>
</ul>
<div class="num-relatedelements"></div>

JavaScript

$(document).ready(function()
                  {
                      $('.2').show();                      
                  });
$(function() {
        
    var numrelated=$('.relatedelements > li:visible').length;
        $('.num-relatedelements').html(numrelated); 
    });