The question is lacking information so I just guess you want to pass some data directly from the controller to your JS code. There are two "normal" ways to do this. The first is to do a direct call to the controller as a http call and return the response as a json. The second method is to pass the data as a class variable, then you can access it in the views folder from the html files. Here you can pass the variable to a div, span or whatever and access it in the JS by finding the html tag in the JS like so:

# controllers: 

def some_controller_method
  @temp = 'example data, could be any type'
end

# views
<%= content_tag :div, class: "some_class", data: {temp: @temp} do %>
<% end %>

# JS
$('.some_class').data('temp')