sections_controller.rb

class SectionsController < ApplicationController
  def update
    section = course.sections.find(params[:id])
    section.update(section_params)

    render section_json(section)
  end

  private

  def section_json(section)
    section_html = render_to_string section, location: nil, formats: [:html]
    section_form_html = render_to_string 'sections/_form', locals: { section: section }, layout: false

    { json: { section_html: section_html, section_form_html: section_form_html } }
  end
end

syllabus.js.coffee

$ ->
  $('#sections-list').on 'ajax:success', 'form.edit_section', Callbacks.reloadSectionAndForm

Callbacks =
  reloadSectionAndForm: (e, json) ->
    parentElement = $(e.delegateTarget)
    Callbacks._replaceFromJson(parentElement, json.section_html)
    Callbacks._replaceFromJson(parentElement, json.section_form_html)
    Callbacks._resetToggles

  _replaceFromJson: (parentElement, html) ->
    element = $(html)
    parentElement.find("##{element.attr('id')}").replaceWith(element)

  _resetToggles: ->
    $('[data-toggle-target]').each ->
      $(@).toggleTarget()