JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <div id="slidable"></div>
    <div id="side">Click me</div>
</div>

CSS

#container{
    width:250px;
    overflow: hidden;
}

#side{
    width:50px;
    height:50px;
    background:#BBB;
    cursor:pointer;
}

#slidable{
    height:50px;
    background:#888;
    width:200px;
    float: right;
}
#slidable.open {
    margin-right: -200px
}

JavaScript

jQuery(document).ready(function($) {
    $( "#side" ).click(function() {
      $( "#slidable" ).toggleClass( "open", 500 );
      });
  });