complicated problem with javascript.

Hello. 'm banging with a difficult problem I think. I have a form like this:

- @company.categorizations.each do |categorization|         %tr           = f.semantic_fields_for :categorizations, categorization do |cat|             %td               %b= categorization.category.name             %td               = cat.input :classification, :as => :select, :collection => Classification.all,                                            :member_label => :classification_type, :label => false,                                            :wrapper_html => { :class => "company_classification" },                                            :input_html => { :class => "company_select_classification_type" }             %td               .company_categorization_amount                 - if categorization.classification                   = text_field_tag "classification_amount", categorization.classification.amount,                                                             :class => "company_input_classification_amount",                                                             :disabled => true                 - else                   = cat.input :amount, :label => false, :wrapper_html => { :class => "company_classification" },                                                         :input_html => { :class => "company_input_classification_amount" }

I hava a coffescript code that monitor the change event of the select field.

$(document).on "change", ".company_select_classification_type", ->     $div = $(this).closest("td").next().find(".company_categorization_amount")     $.get "/classifications/find_amount",     id: $(this).val(), (data) ->       $div.html data

when the select value change I insert in the ".company_categorization_amount" div the code of the file find_amount:

= text_field_tag "classification_amount", @classification.amount, :class => "company_input_classification_amount".

That work. If the select value change and it is blank I want to insert = cat.input :amount. One for every @company.categorizations. I don't know how to do this. Some help?