javascript with awesome_nested_fields

[penchiang]

I need to invoke a javascript function to one of the nested fields. So far, it works well for the field id such as:
$('model_name_attributes_0_fieldname')

However, for the nested field, I have trouble to invoke the javascript using the following id:
$('model_name_attributes_new_nested_item_fieldname')

The page source indicated the above is the correct id. However, it does not work. So, what is the correct id to be used for the nested fields so that I can execute a javascript function?

Can someone help?