I mean that you would have JS in your app/views folder together with the HTML views, instead of the assets folders only. 1. It doesn't depend from RJS/render :

I mean that you would have JS in your app/views folder together with the HTML views, instead of the assets folders only. 1. It doesn't depend from RJS/render :json, but from the fact that your controller responds to sync requests, in addition to the async ones. 2. You can tell to render :json to use server side (erb) partials: render json: { html: render_to_string(partial: 'product') } I do it all the time