JQuery ERB template not inserting HTML

I'm a beginner at JQuery/JS and am trying to implement a dependent drop-down list in a Rails 3.1 app. I have the following form:

<%= debug params %>
<%= form_for([@wall.climbing_centre, @wall]) do |f| %>
  <% if @wall.errors.any? %>
    <div id="error_explanation"> 
      <h2><%= pluralize(@wall.errors.count, "error") %> prohibited this wall from being saved:</h2>

      <ul>
      <% @wall.errors.full_messages.each do |msg| %>
        <li><%= msg %开发者_Go百科></li>
      <% end %>
      </ul>
    </div>
  <% end %>


  <div id="kind" class="field">
    <%= f.label :kind %><br />
    <%= f.select :kind, Wall::Kinds, :input_html => {:rel => "/kinds"} %>
  </div>
  <div class="field">
    <%= f.label :wall_number %><br />
    <%= f.text_field :number%>
  </div>
 <div id="gradelist" class="field">
    <%= f.label :grade  %><br />
    <%= f.select :grade, Wall::BGrades %>
  </div> 

  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

The Following JavaScript

jQuery.ajaxSetup({
 'beforeSend': function(xhr) { xhr.setRequestHeader("Accept", "text/javascript") }
});
jQuery(function($) {
  // when the #kind field changes
  $("#kind").change(function() {
    // make a POST call and replace the content
    $.post('/kinds', {id: $("#wall_kind").val()}, null, "script");
    return false;
  });

})

The following JS.ERB template:

$("#gradelist").html("<%= label :gbabe, 'Grade'%></br><%=select_tag :gbabe, options_for_select(@grades) %>");

The following action in my walls controller: def grades_by_kind

  if params[:id].present?

    @grades = (params[:id] == "Boulder" ? Wall::BGrades : Wall::FGrades)

  else
    @grades = []
  end

  respond_to do |format|
    format.js
  end
end

I have the following constants in the wall model:

FGrades = %w[5 5+ 6A 6A+ 6B 6B+ 6C 6C+ 7A 7A+ 7B 7B+ 8A 8A+ 8B 8B+ 9A 9A+]
BGrades = %w[V0 V0+ V1 V2 V3 V4 V5 V6 V7 V8 V9 V10 V11 V12 V13 V14 15]
Kinds = ['Boulder', 'Leading', 'Top Rope']

Changing a selection in the :kind select box, triggers the JS post request, and receives the following response:

$("#wall_grade").html("<label for="gbabe_Grade">Grade</label></br><select id="gbabe" name="gbabe"><option value="5">5</option>
<option value="5+">5+</option>
<option value="6A">6A</option>
etc...
<option value="8B+">8B+</option>
<option value="9A">9A</option>
<option value="9A+">9A+</option></select>");

However, the drop down values in the id="gradelist" div presented in the webpage aren't actually changing. Why isn't the HTML being changed?

---

Your select isn't changing because you're not doing anything with the response you're getting from the server. You need to specify a callback in your $.post call. Also, you need to convert your grades to an html option list before returning them, perhaps with options_for_select