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
    Introducing MooTools Templated

    One major problem with creating UI components with the MooTools JavaScript framework is that there isn't a great way of allowing customization of template and ease of node creation. As of today, there are two ways of creating: new Element Madness The first way to create UI-driven...

  • By
    Responsive Images: The Ultimate Guide

    Chances are that any Web designers using our Ghostlab browser testing app, which allows seamless testing across all devices simultaneously, will have worked with responsive design in some shape or form. And as today's websites and devices become ever more varied, a plethora of responsive images...

Incredible Demos

  • By
    JavaScript Canvas Image Conversion

    At last week's Mozilla WebDev Offsite, we all spent half of the last day hacking on our future Mozilla Marketplace app. One mobile app that recently got a lot of attention was Instagram, which sold to Facebook for the bat shit crazy price of one...

  • By
    Jack Rugile’s Favorite CodePen Demos

    CodePen is an amazing source of inspiration for code and design. I am blown away every day by the demos users create. As you'll see below, I have an affinity toward things that move. It was difficult to narrow down my favorites, but here they are!

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!