如何在表格中添加行表头？

<table>
  <thead>
    <tr>
      <th>行表头1</th>
      <th>行表头2</th>
      <th>行表头3</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>数据1</td>
      <td>数据2</td>
      <td>数据3</td>
    </tr>
    <tr>
      <td>数据4</td>
      <td>数据5</td>
      <td>数据6</td>
    </tr>
  </tbody>
</table>

table {
  border-collapse: collapse;
}

th, td {
  border: 1px solid black;
  padding: 8px;
}

thead {
  background-color: #f2f2f2;
}

var table = document.querySelector('table');
var thead = table.querySelector('thead');
var newRow = document.createElement('tr');
newRow.innerHTML = '<th>新行表头1</th><th>新行表头2</th><th>新行表头3</th>';
thead.appendChild(newRow);