CKEditor config doesn't change to right-to-left

I have edited config.js to

CKEDITOR.editorConfig = function( config )
{
    // Define changes to default configuration here. For example:
    config.language = 'ar';
    config.contentsLangDirection = 'rtl';
    contentsLanguage:'ar';
    config.dialog_buttonsOrder = 'rtl';
};

But I still get the editor to be left-to-right in my Question2Answer platform. What should I do else to make my editor right-to-left?

Thanks in advance.