<!DOCTYPE html>
<html>
<body>

<p>An unordered list:</p>
<ul>
  <li>Coffee</li>
  <li>Tea</li>
  <li>Milk</li>
</ul>

<p>Click the button to find out how many li elements there are in this document.</p>

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

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

<script>
function myFunction() {
    var x = document.getElementsByTagName("LI");
    document.getElementById("demo").innerHTML = x.length;
}
</script>

</body>
</html>