JSFiddle - React, Tailwind, and code Playground

HTML

<div id="slideleft"></div>
<button>abrir/fechar</button>

CSS

#slideleft {
  width: 200px;
  height: 200px;
  transition: margin-left .5s;
  margin-left: -200px;
  background: #ccf;
}

.abrir {
  margin-left: 0px !important;
}

JavaScript

var button = document.querySelector('button');
var slide = document.querySelector('#slideleft');
button.addEventListener('click', function() {
  slide.classList.toggle('abrir');
})