<!DOCTYPE html>
<html>
<body>
Cats:
<input name="animal" type="checkbox" value="Cats">
Dogs:
<input name="animal" type="checkbox" value="Dogs">
<p>Click the button to find out how many elements there are in the document that have a name attribute with the value "animal".</p>
<button onclick="myFunction()">Try it</button>
<p id="demo"></p>
<script>
function myFunction() {
var x = document.getElementsByName("animal").length;
document.getElementById("demo").innerHTML = x;
}
</script>
</body>
</html>