How to check if atleast one checkbox is checked

I had an issue where I had a list of checkboxes and I needed that after at least one checkbox is clicked to show a div block.

I came up with this:

$(document).ready(function() {
$('input[name=whatever]').change(function() {
  checked = $("input[name=whatever]:checked").length;
  $('#block').hide();
  $('#block2').show();

  if (checked > 0) {
      $('#block').show();
      $('#block2').hide();
  }
});

Code above checks how much there is checked checkboxes and fires the event if at atleast one is checked.

Here is an example in jsfiddle