module ActionView::Helpers::AssetTagHelper::JavascriptTagHelpers::ClassMethods

javascript_include_tag :monkey # =>

ActionView::Helpers::AssetTagHelper.register_javascript_expansion :monkey => ["head", "body", "tail"]

that the plugin installed in public/javascripts.
to be called from plugin initialization to register javascript files
is passed to javascript_include_tag. This method is typically intended
Register one or more javascript files to be included when symbol

def register_javascript_expansion(expansions)
  js_expansions = JavascriptIncludeTag.expansions
  expansions.each do |key, values|
    js_expansions[key] = (js_expansions[key] || []) | Array(values)
  end
end