extract *only* unique values from an existing array

array_unique.js

// private implementation of '[].unique'
Array.prototype.unique = function() {
  var orig = {}
    , i
    , il = this.length
    , res = []
  for (i = 0; i < il; i++) orig[this[i]] = this[i]
  for (i in orig) res.push(orig[i])
  return res
}

usage:

include this snippet in your code and use it like this...
var array_unique = new Array().unique.call(original_array)