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Unique Array Values

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When you look at any programming language, you see missing features that you find puzzling because the use case seems so common.  One such case is retrieving unique values from an array with JavaScript. Years ago I mentioned an easy way of unique value management using objects instead of arrays, but that's not always an option and doesn't match every use case.

Want to retrieve a unique array of values from an array that may include duplicate values?  You can use new JavaScript spread operator with Set to get an array of unique values:

var j = [...new Set([1, 2, 3, 3])]
>> [1, 2, 3]

Getting unique array values is another awesome usage of the spread operator.  And don't forget you can merge object properties with the spread operator!

There's no better feeling than being able to remove a library to complete a task that should be native to the language.  This trick brings us one step closer to that!

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Discussion

  1. Patrick Denny

    If you’re forced to stay in EC5-land without the spread operator, you can use the pollyfillable Array.from()

    var unique = Array.from(new Set([1,2,2,3,3,3,4,5])); // [1,2,3,4,5]
  2. Rob Harris

    Doesn’t seem to work for arrays of objects unless I’m missing something.

    • Muhammad Al Faris

      If your array is an object, you can use map function, to get the value in an array.

      then you can run method like above.

  3. Marcel

    Anybody using babel with this one should be cautious, this will result in an array with a single set element. Patrick Denny’s is the most predictable form.

  4. Cameron

    Thanks David! Very helpful! :)

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