A way to lazy load partials in Rails 4

controller.rb

class Controller
  include LazyLoad

  def show
    @model = Model.find(...)

    respond_to do |format|
      format.html do
        @html_specific_data = Model.find(...)
      end

      render_lazy_load(format) do
        @lazy_specific_data = Model.find(...)
      end
    end
  end
end

helper.rb

module Helper

  def lazy_render(name)
    content_tag :div, :id => "lazy-loaded-#{name.gsub('/', '-')}" do
      content_tag :div, :class => "spinner" do
        content_tag(:script) do
          "if(!window.lazyLoads) { window.lazyLoads = []; }; window.lazyLoads.push('#{name}');".html_safe
        end
      end
    end
  end

end

lazy_load.rb

module PartialLazyLoad
  def render_lazy_load(format, &block)
    format.js do
      block.call if block
      if !params[:search]
        render json: { lazy_load_partial: params[:lazy_load_partial], body: render_to_string(:partial => params[:lazy_load_partial]) } if params[:lazy_load_partial]
      end
    end
  end
end

script.js

<!-- LazyLoad for partials -->
<!-- https://gist.github.com/AlexandrBasan/1c7569ef6f37db4819c2cbe9a2fcc378 -->
<script>
    var i, lazyLoad, len, ref, url, host;

    if (window.lazyLoads) {
        ref = window.lazyLoads;
        for (i = 0, len = ref.length; i < len; i++) {
            lazyLoad = ref[i];
            host = location.protocol + '//' + location.host + location.pathname; // window.location.href.split('#')[0]
            url = host + ("?format=js&lazy_load_partial=" + lazyLoad);
            $.ajax({
                url: url,
                dataType: "json",
                success: function(data) {
                    var element = $("#lazy-loaded-" + data.lazy_load_partial.replace(/\//g, '-'));
                    element.removeAttr('align');
                    return element.html(data.body);
                },
                error: function(JSONHttpRequest, textStatus, errorThrown) {
                    console.log("Status: " + textStatus + ". Error: " + errorThrown);
                    return $("#lazy-loaded-" + lazyLoad.replace(/\//g, '-')).html('<i class="fa fa-ban fa-2x"></i>');

                }
            });
        }
        window.lazyLoads = [];
    }
</script>
<!-- LazyLoad for partials -->

view.html.haml

= render 'foobar'

becomes

= lazy_render 'foobar'