Rails 5 : AJAX variable undefined on ajax:error / ajax:success events

Question

I have a form_with that calls a controller that responds in JSON. I would like to run javascript (handle errors, ...) during an event ajax:success or ajax:error.

I followed the Rails documentation. Unfortunately, the variables in my events are undefined. Only e are set.

Form:

<%= form_with url: contact_path, scope: 'message', id: 'new_message' do |f| %>
    <div class="row">
      <div class="input-field col s6">
        <%= f.text_field :name, class: 'validate' %>
        <%= f.label :name, 'Nom' %>
      </div>
      <div class="input-field col s6">
        <%= f.email_field :email, class: 'validate' %>
        <%= f.label :email, 'Email' %>
      </div>
    </div>
    <div class="row">
      <div class="input-field col s6">
        <%= f.telephone_field :phone, class: 'validate' %>
        <%= f.label :phone, 'Téléphone' %>
      </div>
      <div class="input-field col s6">
        <%= f.text_field :website, class: 'validate' %>
        <%= f.label :website, 'Site Web' %>
      </div>
    </div>
    <div class="row">
      <div class="input-field col s12">
        <%= f.text_area :content, class: 'materialize-textarea validate' %>
        <%= f.label :content, 'Message' %>
      </div>
    </div>
    <div class="row">
      <div class="col s6">
        <%= recaptcha_tags %>
      </div>
      <div class="col s6">
        <%= button_tag class: 'btn primary waves-effect waves-light right' do %>
            Envoyer
            <i class="material-icons right">send</i>
        <% end %>
      </div>
    </div>
<% end %>

Controller:

def create
    @message = Message.new(message_params)

    respond_to do |format|
      if verify_recaptcha(model: @message) && @message.valid?
        MessageMailer.new_message(@message).deliver
        format.json { render json: @message, status: :created }
      else
        format.json { render json: @message.errors, status: :unprocessable_entity }
      end
    end
  end

CoffeeScript:

$(document).ready ->
  $("#new_message").on("ajax:success", (e, data, status, xhr) ->
    console.log(xhr);
  ).on "ajax:error", (e, xhr, status, error) ->
    console.log(xhr);

Result:

undefined  message.self-5eda06948d26dade035273a7f168828c2cb1852e26937c49f50da7ca2532ad72.js:4:14


Started POST "/contact" for 127.0.0.1 at 2017-06-13 17:19:17 +0200
Processing by MessagesController#create as JS
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"aBxh+eJedXw0WifdUXFAlgH0gWxNpiDQa2J3hdJayC/wBaccIxNSVK4pycYwu9XMb1s2/r9S8+FteRFoocdrZQ==", "messages"=>{"name"=>"", "email"=>"", "phone"=>"", "website"=>"", "content"=>""}, "g-recaptcha-response"=>"03AOPBWq9SEfWUxzdyMRMdd0p65vonbGjNjA_mhCA07vfoXyA6_nEVn220Ot5HU90_KpQv6ziii0VCoa1hZosUcsARL7DuJbFHA2kt_NBHvnURmPpKR0SMq0OfulzJokvobdu9t1z33Uby3oTAtTgEAEmxX6yDc_yuwmqHXAjh5SL0bhAyD6AF2wAN8me7fMKMULu_DS5KtLgwJjK8B2TmvGydn0neHDWcfSbDKP7WRP-RQQePc9hDcOCbUFoVrW2kfpg3p4OV-hWiV4q6-HBRZK3A1mcj5rJZd_zBe3v-yx6LHAXB2Bsb9Uc", "button"=>""}
Completed 422 Unprocessable Entity in 2701ms (Views: 0.5ms | ActiveRecord: 856.3ms)

Answer 1

If you are using the rails-ujs adapter, according to this Rails Edge Guide:

Signature of calls to UJS's event handlers has changed. Unlike the version with jQuery, all custom events return only one parameter: event. In this parameter, there is an additional attribute detail which contains an array of extra parameters.

I'd suggest taking a look at your app/assets/javascripts/application.js and find out which ujs adapter you are currently using. //= require rails-ujs is the new default.

Take a look at the example provided in the guide. You can extract data, status, and xhr in the following manner.

document.body.addEventListener('ajax:success', function(event) {
  var detail = event.detail;
  var data = detail[0], status = detail[1],  xhr = detail[2];
})

Another alternative is to to use jquery_ujs which was the default prior to Rails 5.1 and has a signature more like you were expecting.