Firefox warning: mutating the [[Prototype]] of an object will cause your code to run very slowly; instead create the object with the correct initial [[Prototype]] value using Object.create bundle.js:17712

[deathcap]

Firefox 30.0 warns:

TypeError: mutating the [[Prototype]] of an object will cause your code to run very slowly; instead create the object with the correct initial [[Prototype]] value using Object.create bundle.js:17712

    child.__proto__ = parent.__proto__; // line 17712

in function clone(parent, circular), of "clone" module https://www.npmjs.org/package/clone, used in:

clone = require 'clone'
…
  clone: () ->
    return new ItemPile(@item, @count, clone(@tags, false))
…
 splitPile: (n) ->

…
   return new ItemPile(@item, n, clone(@tags, false))