JSFiddle - React, Tailwind, and code Playground

HTML

<button class="showBox">Show</button>
<button class="closeBox">Close</button>

<div class="box hidden"></div>

CSS

.box {
  width: 100px;
  height: 100px;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  background-color: #000;
  display:flex;
  position: absolute;
  animation: slide-in-top 0.5s cubic-bezier(0.25, 0.46, 0.45, 0.94) both;
}

@keyframes slide-in-top {
  0% {
    transform: translateY(-1000px);

    opacity: 0;
  }
  100% {
    transform: translateY(0), translate(-50%, -50%);
    opacity: 1;
  }
}

.hidden {
  display:none;
}

JavaScript

const showBoxBtn = document.querySelector('.showBox');
const closeBoxBtn = document.querySelector('.closeBox');
const box = document.querySelector('.box');

const showBox = function () {
  box.classList.remove('hidden');
}

const closeBox = function () {
  box.classList.add('hidden')
}

showBoxBtn.addEventListener('click', showBox );
closeBoxBtn.addEventListener('click', closeBox);