tabbable.js

/**
 * Add `:tabbable` selector. (From jQuer UI)
 * focusable: https://gist.github.com/Alex1990/f086a23bca98672486ca
 */
$.extend($.expr[':'], {
  tabbable: function(element) {
    var tabIndex = $(element).attr('tabindex');
    var hasTabIndex = tabIndex != null;
    return (!hasTabIndex || tabIndex > 0) && $.expr[':'].focusable(element);
  }
});