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 return the number of tr elements in the table.</p>

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

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

<p id="demo"></p>

<script>
function myFunction() {
    var x = document.getElementById("myTable").rows.length;
    document.getElementById("demo").innerHTML = "Found " + x + " tr elements in the table.";
}
</script>

</body>
</html>