Rails 4: escape_javascript render partial not working

In my Rails 4 app, I am trying to display some views as modals (with Bootstrap modal), instead of the regular .html.erb views.

For instance, I have a calendar model, with a custom analysis action in the controller:

def analysis
  @calendar = Calendar.find(params[:id])
  respond_to do |format|
    format.js
  end
end

Following what is explained in this tutorial and that other tutorial, I am trying to create the following files:

# _dialog.html.erb

<div class="modal fade" id="dialog" tabindex="-1" role="dialog"  aria-labelledby="myModalLabel" aria-hidden="true" data-backdrop="static" data-keyboard="true">
  <div class="modal-dialog">
    <div class="modal-content">
      <div class="modal-header">
        <button type="button" class="close" 
                data-dismiss="modal" 
                aria-label="Close">
                <span aria-hidden="true">&times;</span></button>
        <h3 class="modal-title"></h3>
      </div>
      <div class="modal-body">
      </div>

    </div><!-- /.modal-content -->
  </div><!-- /.modal-dialog -->
</div><!-- /.modal -->

# _analysis.html.erb

<p><%= @calendar.name %> Analysis</p>

# analysis.js.erb

// Add the dialog title
$('#dialog h3').html("Calendar Analysis");

// Render calendar analysis
$('.modal-body').html('<%= j render(:partial => 'calendars/analysis') %>');

// Show the dynamic dialog
$('#dialog').modal("show");

// Set focus to the first element
$('#dialog').on('shown.bs.modal', function () {
    $('.first_input').focus()
  })

Last but not least, I call the modal from a _heading.html.erb partial, rendered inside the calendar show.html.erb view, with the <%= render 'analysis' %> helper and the following link:

<%= link_to '<i class="glyphicon glyphicon-dashboard"></i>'.html_safe, calendar_analysis_path, :remote => true, 'data-toggle' =>  "modal", 'data-target' => '#modal-window' %>

When I launch my app, I then get the following error:

undefined method `render' for #<#<Class:0x007fee248d8118>:0x007fee23577ce0>

—————

UPDATE: I have tried different ways to render the partial:

• As recommended here, I tried both escape_javascript render and j render.
• As recommended there, I have also tried render_to_string instead of just render.
• As recommended in that other question, I even tried different ways to call the partial, both with render(:partial => 'calendars/analysis') and (render 'calendars/analysis').

But none of these solutions worked.

—————

I have done quite a lot of research on that topic and I have to say that I am confused now.

While both tutorials mentioned above recommend this approach, other sources, including this one, point out that you cannot render a partial from assets in Rails.

Therefore:

1. What is wrong with my current code?
2. Does the approach I am trying to use make sense at all, and if not, what shoud I do instead?