数组去重 Removing Duplicate Elements from Arrays

## 问题 Problem 你想给一个数组去重。 You want to remove duplicate elements from an array. ## 方法 Solution ~~~ Array::unique = -> output = {} output[@[key]] = @[key] for key in [0...@length] value for key, value of output [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' ] ~~~ ## 讨论 Discussion JavaScript中有很多中`unique`方法的实现。这里的这个实现基于”The fastest method to find unique items in array”，在[这里](http://www.shamasis.net/2009/09/fast-algorithm-to-find-unique-items-in-javascript-array/)可以找到。 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/). **注意：** 尽管这在常见的语言，比如说Ruby中很常见，但是在JavaScript中扩展原生对象往往被成是不好的实践。(参看： [Maintainable JavaScript: Don’t modify objects you don’t own](http://www.nczonline.net/blog/2010/03/02/maintainable-javascript-dont-modify-objects-you-down-own/); [Extending built-in native objects. Evil or not?](http://perfectionkills.com/extending-built-in-native-objects-evil-or-not/))。 **Note:** Although it’s quite common in languages like Ruby, extending native objects is often considered bad practice in JavaScript (see: [Maintainable JavaScript: Don’t modify objects you don’t own](http://www.nczonline.net/blog/2010/03/02/maintainable-javascript-dont-modify-objects-you-down-own/); [Extending built-in native objects. Evil or not?](http://perfectionkills.com/extending-built-in-native-objects-evil-or-not/)).