JSFiddle - React, Tailwind, and code Playground

HTML

<div id="panel"></div>
<a href="#">open/close</a>

CSS

#panel {
  width:200px;
  height: 200px; 
  background: red;
  display:block;
}

JavaScript

$(function() {
    
    var  myDivWidth = $( "#panel" ).width();
    
    $( "a" ).click(function() {
        if ($( "div#panel" ).width() == 0) {
            $( "div#panel" ).animate({width: myDivWidth}, 'slow');            
        } else {            
            $( "div#panel" ).animate({width: 0}, 'slow'); 
        }     
    });     

});