[Moo] help port jQuery :tabbable/:focusable

[Rolf -nl]

I could use the :tabbable and :focusable selector functions from
jQuery I spotted in jQuery UI,however I have 0 experience in their
language syntax. How would someone start porting stuff like this too a
MooTools extension?

The majority of code is self explaining, but I for instance what
$.attr does .... i dunno...

//Additional selectors
$.extend($.expr[':'], {
  data: function(elem, i, match) {
    return !!$.data(elem, match[3]);
  },

  focusable: function(element) {
    var nodeName = element.nodeName.toLowerCase(),
      tabIndex = $.attr(element, 'tabindex');
    return (/input|select|textarea|button|object/.test(nodeName)
      ? !element.disabled
      : 'a' == nodeName || 'area' == nodeName
        ? element.href || !isNaN(tabIndex)
        : !isNaN(tabIndex))
      // the element and all of its ancestors must be visible
      // the browser may report that the area is hidden
      && !$(element)['area' == nodeName ? 'parents' : 'closest']
(':hidden').length;
  },

  tabbable: function(element) {
    var tabIndex = $.attr(element, 'tabindex');
    return (isNaN(tabIndex) || tabIndex >= 0) && $(element).is
(':focusable');
  }
});