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 change the content of the first table cell.</p>

<table id="myTable">
  <tr>
    <td>Row1 cell1</td>
    <td>Row1 cell2</td>
  </tr>
  <tr>
    <td>Row2 cell1</td>
    <td>Row2 cell2</td>
  </tr>
  <tr>
    <td>Row3 cell1</td>
    <td>Row3 cell2</td>
  </tr>
</table>
<br> 

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

<script>
function myFunction() {
    var x = document.getElementById("myTable").rows[0].cells;
    x[0].innerHTML = "NEW CONTENT";
}
</script>

</body>
</html>