Topic: dynamic menu via AJAX

hello, im implementing a Category and subcategory. However, it archieve it using only 1 model with the gem 'awesome_nested_set' ,so when i click my first collection_Select,it will process my ajax and return a instant variable for my controller and get the category for the second collection select.
I almost done it ,but left some little problem,

1. when i load the page , it give me error "might expect an instant of array"
i knw why this come from ,its because ,when i load the page ,it actually load the js, but initialy, i havent click the first collection_select,do i cannot get the value from the select and my controller cannot get the params from there too.
2.i did try to dont run the partial ,but my firebug console show me red color ,but i see it can get the params from the first collection_select edy.

Here is my gist.gihub
full code is provided, please guide me ,i need some modification then can do it edy.. @@

Last edited by eleventwice9 (2012-06-30 01:37:51)