JSFiddle - React, Tailwind, and code Playground

HTML

<button type="button" onclick="Mudarestado('formulario')">
  Abrir div
</button>
<form id="formulario" action=" ">
  <input type="text ">
  <input type="text ">
</form>

CSS

#formulario {
  transition: margin-left 1.5s;
  border: 1px solid #ccf;
  padding: 1em;
  width: 10em;
  margin-left: -15em;
}

#formulario.mostrar {
  margin-left: 0em;
}

JavaScript

function Mudarestado(el) {
  document.getElementById(el).classList.toggle('mostrar');
}