<!DOCTYPE html>
<html>
<head>
<style>
table, td {
    border: 1px solid black;
}

</style>
</head>
<body>

<p>Click the button to alert the innerHTML of the first tbody element (index 0) in the table.</p>

<table id="myTable">
<tbody>
  <tr>
    <td>cell 1</td>
    <td>cell 2</td>
  </tr>
</tbody>
<tbody>
  <tr>
    <td>cell 3</td>
    <td>cell 4</td>
  </tr>
</tbody>
</table>
<br>

<button onclick="myFunction()">Try it</button>

<script>
function myFunction() {
    alert(document.getElementById("myTable").tBodies.item(0).innerHTML);
}
</script>

</body>
</html>