JSFiddle - React, Tailwind, and code Playground

HTML

<div id="blah" style="display:none;">
    <div style="width: 20px; height: 20px; border: #c0c0c0 solid 1px;">
    </div>
</div>

<input type="button" id="click" value="click"/>

JavaScript

$("#click").click(function() {

          $("#blah").slideToggle('slow', function() {
              var flipout = this;

              if (flipout.style.display == "block") { 
                  alert("block");
              } 
              else {   
                  alert("not block");
              }   
          });
      });