<div id="list">
  <h2>Animals</h2>
</div>
html, body {
  height: 100%;
}

body {
  display: grid;
  justify-content: center;
  align-content: center;
}
const animals = ['cat', 'dog', 'mouse']

const list = `
<ul>
  <li>${animals[0]}</li>
  <li>${animals[1]}</li>
  <li>${animals[2]}</li>
</ul>`

const $list = document.getElementById('list')
$list.insertAdjacentHTML('beforeend', list)
$list.insertAdjacentHTML('afterbegin', `<h4>a list of</h4>`)

External CSS

  1. https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.1.3/css/bootstrap.min.css

External JavaScript

This Pen doesn't use any external JavaScript resources.