JSFiddle - React, Tailwind, and code Playground

HTML

<div id="panel"></div>

CSS

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

JavaScript

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

    $( "div#panel" ).animate({width: 0}, 'slow');

});