How to render format JavaScript in a Rails controller

Question

I have a route called "/admin", which is used to add and list products, from:

resources :products, controller: "admin"

In the controller admin I have a create function:

  def create
    @product = Product.new product_values
    respond_to do |format|
      if @product.save
        format.html { redirect_to :root }
      else
        format.js { render 'admin/error' }
      end
    end
  end

When I tried to make it render to format.js, it said:

ActionController::UnknownFormat
on `respond_to do |format|`

I thought created admin/create.js.haml:

console.log("got it")

but it doesn't work.

Why did I want the response to be "format.js"? Because I want to add an error message to the form and don't want to refresh the page, so I respond to the JavaScript to append on some div with the error message.

This is admin/add_product.html.haml:

.p-5
  .container.column.justify-content-center
    %div.d-flex.justify-content-center.p-4#this-error
      %div
        %h3
          Add Product
    %div
      = form_for (@product || Product.new) do |f|
        .form-group.row
          = f.label :name,  class: 'col-md-2 col-form-label'
          %br/
          .col-sm-8
            = f.text_field :name, class: 'form-control'
        .form-group.row
          = f.label :stock,  class: 'col-md-2 col-form-label'
          %br/
          .col-sm-2
            = f.number_field :stock, class: 'form-control'
          .my-4
          = f.label :price,  class: 'ml-5 col-md-1 col-form-label'
          %br/
          .col-sm-2
            = f.number_field :price, class: 'form-control'
        .form-group.row
          = f.label :desc,  class: 'col-md-2 col-form-label'
          %br/
          .col-sm-8
            = f.text_area :desc, class: 'form-control'
        .d-flex.justify-content-center
          = f.submit "Add", class: 'btn btn-primary col-sm-8 p-2'

How do I use format.js in Haml for this?

format.html is handler for html request and format.js is handler for ajax request. You must be submitting form normally instead of AJAX and so get this error. Share your haml code as well. — Amit Patel
– Amit Patel, Commented Apr 4, 2020 at 12:59
i want to add error message on id: #this-error so I that is why I need to use javascript to not refresh the page when the forms is empty, so when i submit "Add" the form empty and must get error message — jhgju77
– jhgju77, Commented Apr 4, 2020 at 13:11
Add remote: true to the form if you want to make an ajax request — arieljuod
– arieljuod, Commented Apr 4, 2020 at 14:59

Sohail Aslam · Accepted Answer · 2020-04-04 13:44:33Z

1

You are submitting a local request through the form, not remote (AJAX request) so your

format.js

will never be called.

what you can do is:

def create
    @product = Product.new product_values
    respond_to do |format|

        format.html { 
          if @product.save
             redirect_to :root
          else
             render 'admin/error'
           end
           }
        format.js {  }

    end
  end

answered Apr 4, 2020 at 13:44

Sohail Aslam

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