JavaScript asset helper. Forked from https://gist.github.com/patrickberkeley/3879730, cleaned up the assignment to "images" in the App.assets object to not have an extra comma and to be a single line.

assets.js.erb

App.assets = {
  // Returns an object containing all of asset pipeline's image paths.
  //
  // Sample:
  //
  // {
  //   avatars/missing_avatar.png: "/assets/avatars/missing_avatar.png"
  //   chosen-sprite.png: "/assets/chosen-sprite.png"
  //   circle_green.png: "/assets/circle_green.png"
  //   circle_orange.png: "/assets/circle_orange.png"
  //   circle_red.png: "/assets/circle_red.png"
  //   circle_yellow.png: "/assets/circle_yellow.png"
  //   document.png: "/assets/document.png"
  // }
  //
  images: <%= (AssetsUtil.images.inject({}){|hash,img| hash[img] = asset_path(img);hash}.to_json) %>,

  // Return a formatted URL for an asset.
  //
  // Sample:
  //
  // "/assets/document/png."
  //
  path: function(name) {
    // If the file is in our images object, pull the path from there.
    if (this.images && this.images[name]) {
      return this.images[name];
    }

    // Otherwise, create a generic asset path.
    return '/assets/' + name;
  }
}

assets_util.rb

module AssetsUtil
  def self.images
    Dir.glob(Rails.root.join("app/assets/images/**/*.*")).map do |path| 
      path.gsub(Rails.root.join("app/assets/images/").to_s, "")
    end
  end
end

example.ejs.jst

<div class="example">
  <img src="<%= App.assets.path('bookmarklet/add.png') %>">
<div>