JSFiddle - React, Tailwind, and code Playground

HTML

<div id="gallery">
    <ul>
        <li>this</li>
        <li>this</li>
        <li>that</li>
        <li>this</li>
        <li>that</li>        
        <li>that</li>
    </ul>
</div>

CSS

#gallery ul {
display:block;
position:relative;
width:14000px;
background: #f00;
}

JavaScript

setTimeout(function(){
   var posVar = 2838+'px';        
   $('#gallery ul').css("right", '-14000px');
},300);