Rails: don't refresh page after modal action/submit

I have a modal which opens on top of another screen. The base screen has a filter method that uses AJAX to filter the results on that page.

After, I filter the results on the screen, I can open the modal and perform an action on the form in the modal. However, I don't want to perform a redirect/refresh.

How do I do this while still performing the submission?

My modal link is like:

<%= link_to this_path(user_id: user.id), class:"modal-link", data: {"modal-url" => this_path(user_id: user.id)} do %><span><i class="fa fa-plus"></i><% end %>

The modal is standard enough:

<div class="modal form-modal">
    <div class="modal-container">
        <div class="modal-dialog modal-dialog-wide">
            <button class="close">&times;</button>
            <div class="modal-content">
                <div class="modal-header">
                    <h2 class="hdg-b">Edit This</h2>
                </div>
                <div class="modal-body">
                    <div id="error_explanation"></div>
                    <%= render 'form', form_path: action_path, form_method: :put, create: false %>
                </div>
            </div>
        </div>
    </div>
</div>

The AJAX is too:

MyProject.onPageLoad(function() {
  var form  = $('.edit_site_scope'),
  onSubmit  = function(event) {     //callback handler for form submit
                event.preventDefault();
                var form     = $(this),
                url          = form.attr("action"), //get form action:
                type         = form.attr("method"),
                data         = form.serialize();
                var location = window.location.href;

                var posting  = $.ajax({
                  type: type,
                  url: url,
                  data: data,
                  dayaType: "json",
                  success:function(data, textStatus, jqXHR) 
                  { 
                    $('.modal').remove();
                    window.location = location;
                    $('#contact-tab-submit').show();
                  },
                  error: function(jqXHR, textStatus, errorThrown) 
                  {
                    $('#error_explanation').html('');
                    errors = jqXHR.responseJSON;
                    $.each( errors, function( key, value ) {
                      $('#error_explanation').append('<div class="alert alert-dismissable" id="alert-message"><i class="fa fa-exclamation-triangle"></i>' + value + '<div class="alert-close">Close</div></div>');
                    });
                    $('#contact-tab-submit').show();
                  }
                });

                window.setTimeout(function() {
                  $(".alert").fadeTo(500, 0).slideUp(500, function(){
                      $(this).remove(); 
                  });
                }, 5000);

                retu false; // prevent default when submit button clicked
  };
  if (form.size() !== 0)  {
      form.submit(onSubmit);
  }
});

And here is my controller action on the form submit:

def action_to_be_performed
    @this_thing = ThisThing.where(id: params[:id]).first
    @this_thing.update(this_things_params)
    flash[:success] = "Successfully performed the action."
    render json: @this_thing
  rescue => error
    Rails.logger.error "Exception caught updating user study site scope.nCause: #{error}n" + error.backtrace.join("n")
    render json: @this_thing.errors.full_messages, status: :bad_request
  end

I really struggle with modals still and I guess with AJAX. How do I perform my action, close the modal and keep the current page open?