Extending Backbone collections

Batbone-excerpt.coffee

@LIST = (path="", model=null, opts={}) ->
  opts.model = model if model
  Backbone.Collection.extend $.extend opts,
    parse: ({data}) -> data
    comparator: (item) ->
      compare_item(item)
    url: API path       
@REVERSE_LIST = (path="", model=null, opts={}) ->
  list = @LIST(path, model, opts)
  $.extend list,
    comparator: (item)->
      value = -compare_item(item)
      value
  list

Batbone-excerpt2.coffee

@LIST = (path="", model=null, opts={}) ->
  opts.model = model if model
  Backbone.Collection.extend $.extend opts,
    parse: ({data}) -> data
    comparator: (item) ->
      compare_item(item)
    url: API path       
@REVERSE_LIST = (path="", model=null, opts={}) ->
  list = @LIST(path, model, opts)
  # extend does not modify list in place
  list.extend comparator: (item)->
      value = -compare_item(item)
      value
  # This returns the original version of list, not the extended one
  list 

Batbone-excerpt3.coffee

@REVERSE_LIST = (path="", model=null, opts={}) ->
  @LIST(path, model, opts).extend comparator: (item)->
    -compare_item(item)

@REVERSE_LIST = (path="", model=null, opts={}) ->
  opts.model = model if model
  Backbone.Collection.extend $.extend opts,
    parse: ({data}) -> data
    comparator: (item) ->
      -compare_item(item)
    url: API path