Unknown Format error with respond_to in Rails. Correctly trying to implementing polling-to-update

You can try a shortcut like respond_to :html, :js and see if that clears it up. Otherwise try something more explicit:

def show  @simulation = Simulation.find(params[:id])  respond_to do |format|    format.js { render: "some view"}    format.html { redirect_to simulation_url }  endend

format.js in the :show action will by default render show.js.erb when show is called with ajax. The html response will be a redirect.

This blog post may be helpful.

Perhaps issue is with whatever calls the show action in the first place,and it's missing the remote: true option ?

If its a link then try with remote: true option, something like :

<%= link_to 'Show', simulation_path(my_simulation), remote: true %>

same if its a button

<%= button_to 'Show', simulation_path(my_simulation), remote: true %>

This should cause Rails to call the controller with correct format and in logs you should see JS mentioned, e.g.

Processing by SimulationsController#show as JS

Also in the partial you are probably missing the dataType, try :

$.ajax({    type: "PUT",    url: "/simulations/#{params}",    dataType: "script"})