Unique Array Values

By  on  

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!

Recent Features

  • By
    Designing for Simplicity

    Before we get started, it's worth me spending a brief moment introducing myself to you. My name is Mark (or @integralist if Twitter happens to be your communication tool of choice) and I currently work for BBC News in London England as a principal engineer/tech...

  • By
    CSS vs. JS Animation: Which is Faster?

    How is it possible that JavaScript-based animation has secretly always been as fast — or faster — than CSS transitions? And, how is it possible that Adobe and Google consistently release media-rich mobile sites that rival the performance of native apps? This article serves as a point-by-point...

Incredible Demos

  • By
    Comment Preview Using MooTools

    Comment previewing is an awesome addition to any blog. I've seen really simple comment previewing and some really complex comment previewing. The following is a tutorial on creating very basic comment previewing using MooTools. The XHTML You can set up your XHTML any way you'd like.

  • By
    Truly Responsive Images with responsive-images.js

    Responsive web design is something you hear a lot about these days. The moment I really started to get into responsive design was a few months ago when I started to realise that 'responsive' is not just about scaling your websites to the size of your...

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. 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. Thanks David! Very helpful! :)

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!