Add javascript to get the value of checkbox or select box

You can also use the below code to get all checked checkboxes values.

1. <script>
2. document.getElementById('btn').onclick = function()
3. var markedCheckbox = document.querySelectorAll('input[type="checkbox"]:checked');
4. for (var checkbox of markedCheckbox)
5. document.body.append(checkbox.value + ' ');
6. </script>