add recipe Removing duplicate elements from Arrays

Author: phlipper

chapters/arrays/removing-duplicate-elements-from-arrays.md

@@ -0,0 +1,26 @@
+---
+layout: recipe
+title: Removing duplicate elements from Arrays
+chapter: Arrays
+---
+## Problem
+
+You want to remove duplicate elements from an array.
+
+## Solution
+
+{% highlight coffeescript %}
+Array::unique = ->
+  o = {}
+  r = []
+  o[this[i]] = this[i] for i in [1...@length]
+  r.push(v) for k,v of o
+  r
+
+[1,1,2,2,2,3,4,5,6,6,6,"a","a","b","d","b","c"].unique()
+# => [ 1, 2, 3, 4, 5, 6, 'a', 'b', 'd', 'c' ]
+{% endhighlight %}
+
+## Discussion
+
+There are many implementations of the `unique` method in JavaScript. This one is based on "The fastest method to find unique items in array" found [here](http://www.shamasis.net/2009/09/fast-algorithm-to-find-unique-items-in-javascript-array/).