Ruby on Rails - Send JavaScript variable from controller to external Javascript asset file

Question

I am creating a website in Ruby on Rails. I have a controller action that renders a view like so:

def show
  time_left = Time.now.to_i - 3.hours.to_i
  @character = current_user.characters.find(params[:id])
  respond_to do |format|
    format.html # show.html.erb
    format.xml  { render :xml => @character }
  end
end

This is fine as it renders the show.html.erb as I like. I would like however to somehow pass time_left to the view as a Javascript variable as this value is use by a countdown JQuery plugin.

I could put a javascript block on the page in the HTML and print a instance variable out like so:

<script type="javascript"> $('#countdown').countdown('<%= @time_left =>')</script>

But I would like to keep all my JS in a external file and off the page could anyone give some advice on how to implement this?

Answer 1

Yes, you can!

Rewrite your JS code into function with one argument (timelimit) and put it into some external file. Then you can call the function from view and pass that @timeleft variable as JS function argument.

Short example:

#controller
@time_left = Time.now.to_i - 3.hours.to_i

.

#javascript
function count_down(time_left) {
  $('#countdown').countdown(time_left)
}

.

#view
<%=javascript_tag "count_down(#{@time_left})" -%>

javascript_tag

Example not tested, it is only idea not complete solution. Don't forget to load that JS file. You can use other JS rails helper javascript_include_tag.