Controller action respond_to format error ActionController::UnknownFormat

I have an issue with controller action respond in Ruby on rails app.

So, I have two actions in my taskasset_controller with simple code:

  def destroy

    if params[:id].present?
      @asset = TaskAsset.find(params[:id])
      authorize @asset, :destroy?

      @asset.destroy

      respond_to do |format|
        format.js { @asset.id }
      end
    end
  end



 def create
    @task = Task.find(params[:task_id])
    authorize @task

    respond_to do |format|
      if params[:images]
        params[:images].each { |image|
          @task.task_assets.create(image: image)
        }
      end
        @task_assets = @task.task_assets
        authorize @task_assets, :create?

      format.js { @task_assets }
    end
  end

Also I have regulary created two forms destroy.js.erb and create.js.erb and in case of destroy when I delete image from form I got respond id of deleted image so that info I am using to hide modal preview of image.

But in case of create action I am getting error about:

ActionController::UnknownFormat
Extracted source (around line #14):

    authorize @task

    respond_to do |format|
      if params[:images]
        params[:images].each { |image|
          @task.task_assets.create(image: image)

What em I missing in case of create action respond format?

So solution in my case was:

 **<script src="http://malsup.github.com/jquery.form.js"></script>**

 **<%= form_for TaskAsset.new, url: task_assets_path(format: :js),remote: true, :html => {remote: true, :multipart => true,id: 'ajaxformtask'  } do |form| %>**

   <%= hidden_field_tag :authenticity_token, form_authenticity_token %>

   <%= hidden_field_tag 'task_id', task.id %>
   <div class="form-group">
   <div class="col-md-12">
     <label>Select Images</label>
     </div>
     <%= file_field_tag "images[]", id: "imageUploadInput", type: :file, multiple: true, class:'form-control display-block' %>
   </div>

   <div class="actions">
   <div class="padding-bottom-3x text-center">

     <button type="button" id="cancel-add-task-assets" class="btn btn-lg btn-warning">Cancel</button>
     <%= form.submit "Save", id:"add-task-assets", class: 'btn btn-lg task-btn-color' %>
     </div>
   </div>
 <% end %>

 **<script>
   $(document).ready(function(){
       $("#ajaxformtask").ajaxForm()
   })
 </script>** 

1. Adding script: http://malsup.github.com/jquery.form.js into project here is only example where we put it on partial view.

2. Adding form ID name and (format: :js)

   {remote: true, :multipart => true,id: 'ajaxformtask' } do |form| %>

3. Adding:

   $(document).ready(function(){ $("#ajaxformtask").ajaxForm() })

Here is also final look of create controller action:

def create

     @task = Task.find(params[:task_id])
     #@task = policy_scope(@venue.tasks).find(params[:task_id]).decorate
     #authorize @task
     if params[:images]
       params[:images].each do |image|
         @task.task_assets.create(image: image)
       end
     end
     @task_assets = @task.task_assets
     authorize @task_assets, :create?

     @result  = [@task_assets, @venue]

     respond_to do |format|
         format.json { @task_asset.to_json }
         format.js{ @result }
           #format.js {render js: 'alert("success")'} # now you cann append that image to te image list here or create create.js.erb ...ok I have that alreday let try
       end

   end