Tryit Editor v2.9

Edit This Code:
<!DOCTYPE html>
<html>
<head>
<style>
table, td {
    border: 1px solid black;
}
</style>
</head>
<body>

<p>Click the button to insert new cell(s) at the index position 2 of the table row.</p>

<table>
  <tr id="myRow">
    <td>First cell (index 0)</td>
    <td>Second cell (index 1)</td>
    <td>Third cell (index 2)</td>
  </tr>
</table><br>

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

<script>
function myFunction() {
    var row = document.getElementById("myRow");
    var x = row.insertCell(2);
    x.innerHTML = "New cell";
}
</script>

</body>
</html>