function attemptFocus(el) {
      if (el && el.getAttribute('tabindex') != -1) {
        el.focus();
        return ($document[0].activeElement == el);
      }
    }
Attempts to focus an element. Checks whether that element is the currently
focused element after attempting.
@param {HTMLElement} el - the element to attempt focus on
@returns {boolean} - whether the element was successfully focused