Very similar to the legacy example, but uses the callback style instead. Format the output with blank-padded value for weeks (%-w) and days (%-d) and pluralize it’s output with %!w and %!d.
  This plugin will be available in ...
  
HTML:
<div id="clock"></div>JS:
$('#clock').countdown('2020/10/10').on('update.countdown', function(event) {
  var $this = $(this).html(event.strftime(''
    + '<span>%-w</span> week%!w '
    + '<span>%-d</span> day%!d '
    + '<span>%H</span> hr '
    + '<span>%M</span> min '
    + '<span>%S</span> sec'));
});