SOURCE

// setTimeout(() => {
//   el.style.display = 'none';
// },
// 100);

function showPTag() {
  const el = document.getElementById('box');
  const map = {none: 'block', block: 'none'};
	el.style.display = map[el.style.display];
}

<div id="box" style="display: block;">
  <p class="zoom">
    11112222233333
  </p>
</div>
<button onclick="showPTag()">
  显示
</button>

#box {
  padding: 15px;
  background: #ccc;
  display:block;
}

.zoom {
  animation: zoom 3000ms ease-in-out;
}

@keyframes zoom {
  0% {
    opacity: 0;
    transform: scale(1.1);
  }
  100% {
    opacity: 1;
    transform: none;
  }
}