<!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>