Simple localstorage polyfill

localstorage.coffee

################################################################################
#
# [global] localstorage
# A simple cookie based polyfill for localStorage 
#
################################################################################
unless Modernizr.localstorage
  window.localStorage =
    length: 0
    setItem: (key, value) ->
      days = 365
      date = undefined
      expires = undefined
      if days
        date = new Date()
        date.setTime date.getTime() + (days * 24 * 60 * 60 * 1000)
        expires = "; expires=" + date.toGMTString()
      else
        expires = ""

      document.cookie = key + "=" + value + expires + "; path=/"
      @length++

    getItem: (key) ->
      keyEQ = key + "="
      ca = document.cookie.split(";")
      i = 0
      len = ca.length

      while i < len
        c = ca[i]
        c = c.substring(1, c.length)  while c.charAt(0) is " "
        return c.substring(keyEQ.length, c.length)  if c.indexOf(keyEQ) is 0
        i++
      null

    #
    # Todo: add listAllItems api.
    #

    removeItem: (key) ->
      @setItem key, "", -1
      @length--

    clear: ->
      
      # Caution: will clear all persistent cookies as well
      ca = document.cookie.split(";")
      i = 0
      len = ca.length

      while i < len
        c = ca[i]
        c = c.substring(1, c.length)  while c.charAt(0) is " "
        key = c.substring(0, c.indexOf("="))
        @removeItem key
        i++
      @length = 0

    key: (n) ->
      ca = document.cookie.split(";")
      return null  if n >= ca.length or isNaN(parseFloat(n)) or not isFinite(n)
      c = ca[n]
      c = c.substring(1, c.length)  while c.charAt(0) is " "
      c.substring 0, c.indexOf("=")