Jquery plugin for adding and removing nested records (Rails accepts nested attributes for)

example.erb.html

<!-- Sorry, this example is with formtastic but I think it would work the same with vanilla rails form helpers -->



<%= semantic_form_for @survey do |form| %>
  <fieldset class="nested_models answers" data-association="answers">
    <%- form.object.answers.build %>
    <%= form.semantic_fields_for :answers do |answer| %>
      <%- record = answer.object %>
      <fieldset class="<%= record.new_record? ? :new : nil %>">
        <ol>
          <%= answer.input :text, required: false %>
          <%= answer.input :_destroy, as: :boolean %>
        </ol>
      </fieldset>
    <% end %>
    <%= link_to t('.add_answer'), '#', :class => 'add_record', :style => 'display:none' %>
  </fieldset>
  <%= form.buttons do %>
    <%= form.commit_button %>
  <% end %>
<% end %>


<script>
  $('fieldset[data-association]').nestedAssociations();
</script>

jquery.nested-associations.js

// macario ortega
// github.com/maca
// mit licence

(function($){
  $.fn.nestedAssociationsChangeId = function(association, newId){
    $(this).find('[id], [for], [name]').each(function(){
      var tag = $(this);
      $.each(['id', 'for', 'name'], function(index, attribute){
        var value = tag.attr(attribute);

        if (value && attribute == 'name') { 
          var matcher = new RegExp('\\[' + association + '_attributes\\]\\[\\d+\\]');
          tag.attr(attribute, value.replace(matcher, '[' + association + '_attributes][' + newId + ']'));
        } else if (value) {
          var matcher = new RegExp(association + '_attributes_\\d+');
          tag.attr(attribute, value.replace(matcher, association + '_attributes_' + newId)); 
        }; 
      });
    });
  };

  $.fn.nestedAssociations = function(opts){
    var self = $(this);
    var associationFieldset = self;
    var settings = {
      add    : $.noop,
      remove : $.noop
    }
    if (opts) { $.extend(settings, opts); }

    $(this).find('input[id$=_destroy]').closest('label').each(function(){
      var destroyLink  = $('<a href="#" class="remove-associated-record">').text($(this).text());
    
      destroyLink.click(function(){
        $(this).siblings('input').attr('value', '1');
        settings.remove.apply($(this).closest('fieldset').slideUp());
        return false;
      });

      $(this).hide().after(destroyLink);
    });

    return associationFieldset.each(function(){
      var container    = $(this);
      var association  = container.attr('data-association');
      var template     = container.children('fieldset.new').last().detach();

      container.children('a.add_record').show().click(function(){
        var cleanTemplate = template.clone(true);
        $(this).before(cleanTemplate.hide());

        $(this).parents('fieldset[data-association]').each(function(){
          var association = $(this).attr('data-association');
          $(this).children('fieldset.new').each(function(){
            $(this).nestedAssociationsChangeId(association, new Date().getTime());
          })
        });

        cleanTemplate.slideDown(function(){
          settings.add.apply(this);
        });
        return false;
      });
    });
  };
})(jQuery);