Using Array.prototype.sort to implement a stable sort

stableSort.coffee

define [], () ->
  Array.prototype.unstableSort = Array.prototype.sort

  Array.prototype.sort = (compareFn) ->
    compareFn ?= (a, b) -> a?.toString?()?.localeCompare?(b?.toString?()) || 0

    list = ({ pos: i, val: v} for v, i in this)

    list.unstableSort (a, b) ->
      comp = compareFn(a.val, b.val)
      return a.pos - b.pos if comp == 0
      return comp

    this[..] = (v.val for v in list)
    return this