public static function addSystemScript($script, $dir = 'js')
	{
		if ($dir != 'js')
		{
			$script = $dir . '/' . $script;
		}

		$asset = new Javascript('system', $script);

		if ($asset->exists())
		{
			if ($document = self::app('document'))
			{
				$document->addScript($asset->link());
			}
		}
	}