Edit in JSFiddle

<table>
  <tr>
    <th>Firstname</th>
    <th>Lastname</th>
    <th>Born</th>
  </tr>
  <tr>
    <td>Jean</td>
    <td>Lamarck</td>
    <td>1744</td>
  </tr>
  <tr>
    <td>Charles</td>
    <td>Darwin</td>
    <td>1809</td>
  </tr>
</table>

const $table = document.querySelector('table')
const $$tr = [...document.querySelectorAll('tr:not(:first-child)')]

document.querySelectorAll('th').forEach($th => {
  $th.onclick = e => {
    const i = e.target.cellIndex
    $$tr.sort((a, b) => {
      a = a.querySelector(`:nth-child(${i + 1})`).textContent
      b = b.querySelector(`:nth-child(${i + 1})`).textContent

      return Intl.Collator().compare(a, b)
    }).forEach($tr => $table.appendChild($tr))
  }
})

th:hover {
  cursor: pointer;
  color: orange;
}