Using a Rails helper method within a javascript asset

Is there any way to use a Rails helper method, more specifically, a path helper method within a javascript asset file. This file

$('#bar').val("<%= create_post_path %>")

I would love it if I could get from erubis




You can include any helper/module/class in an erb template with:

<% environment.context_class.instance_eval { include MyHelper } %>

See: and

To use the url helpers you have to include your specific applications' helpers.

They are available at Rails.application.routes.url_helpers so:

<% environment.context_class.instance_eval { include Rails.application.routes.url_helpers } %>

EDIT: Fixed links to moved sprockets repo but not really sure this still makes sense so many years later.


This will also do the trick in an initializer:

Sprockets::Context.send :include, MyHelper

In development mode the helper will not be reloaded on every request.

Your approach with UrlHelpers will work until you need to find post_path( don't know what post id we'll need at compile time...). There is a ruby gem which reimplements all of your Rails UrlHelpers in JavaScript:


Indeed I agree with @eirc answer (taking into account Sprockets documentation). But I would consider including helper modules at rails boot time. As per

# config/initializers/sprockets.rb
Rails.application.assets.context_class.instance_eval do
  include ActionView::Helpers
  include Rails.application.routes.url_helpers
  include MyModule

this is because of:


Actually, not sure if this helps but there is a way to define your own helpers for use during rake precompile

Create a new initializer and put this in it:

module Sprockets
  module Helpers
    module RailsHelper

      def my_helper_method


And then you can:

<%= my_helper_method %>

in your .erb assets


I'm not quite sure, why you want to do this.

  • You would prevent the javascript file from being cached, as it contains a dynamic value

  • You would get a coupling between your javascript/coffeescript and rails

If possible I would advice you to abstract your problem away by providing your target path in the view and retrieve the value from the DOM-Element when the specific event occurs. Just like 'Unobtrusive Scripting Adapters' for Rails do. E.g.:


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