Using a Rails helper method within a javascript asset

Question

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

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

I would love it if I could get from erubis

$('#bar').val("path/to/create") 

Answer 1

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

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

See: https://github.com/rails/sprockets/blob/master/lib/sprockets/environment.rb and https://github.com/rails/sprockets/blob/master/lib/sprockets/context.rb

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.

Answer 2

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(...um...we 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: https://github.com/railsware/js-routes