LazilyExtensible.coffee

require 'harmony-reflect'

LazilyExtensible = (obj) ->
  switch typeof obj
    when 'object', 'function'
      Proxy obj,
        get: (target, name) ->
          if target[name] is undefined
            target[name] = LazilyExtensible {}
          else
            target[name]
    else
      obj


obj = LazilyExtensible { a: 1 }
console.log obj.a # => 1

obj.b.c = 2
console.log obj.b.c # => 2

obj[123][456][789] = (value) -> @abc.def.ghi = value
obj[123][456][789] 'foobar'
console.log obj[123][456].abc.def.ghi # => "foobar"