Uncaught TypeError: Cannot read property 'settings' of undefined

Hi,
I'm having this issue

Uncaught TypeError: Cannot read property 'settings' of undefined

I like the way we use the CSS Classes.
at this code

(function($) {
  Drupal.behaviors.selectize = {
    attach: function(context, settings) {
      if (typeof settings.selectize.settings != 'undefined') {
        $.each(settings.selectize.settings, function(index, value) {
          $('#' + index).selectize(JSON.parse(value));
        });
      }
    }
  }
})(jQuery);

But seems that it's not worked out in the right way.
Not sure we may need to add ( Classes as we add IDs ) .

Thanks.