Ordered hash in JavaScript

Question

JavaScript objects have no order stored for properties (according to the spec). Firefox seems to preserve the order of definition of properties when using a for...in<

Answer 1

This question come up as the top search result. After not finding a ordered hash, i just wrote this small coffescript. Hopefully this will help folks landing on this page:

## OrderedHash
# f = new OrderedHash
# f.push('a', 1)
# f.keys()
# 
class OrderedHash
 constructor: ->
   @m_keys = []
   @m_vals = {}

  push: (k,v) ->
    if not @m_vals[k]
      @m_keys.push k
    @m_vals[k] = v

  length: () -> return @m_keys.length

  keys: () -> return @m_keys

  val: (k) -> return @m_vals[k]
  vals: () -> return @m_vals