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
    5 HTML5 APIs You Didn’t Know Existed

    When you say or read "HTML5", you half expect exotic dancers and unicorns to walk into the room to the tune of "I'm Sexy and I Know It."  Can you blame us though?  We watched the fundamental APIs stagnate for so long that a basic feature...

  • By
    An Interview with Eric Meyer

    Your early CSS books were instrumental in pushing my love for front end technologies. What was it about CSS that you fell in love with and drove you to write about it? At first blush, it was the simplicity of it as compared to the table-and-spacer...

Incredible Demos

  • By
    Fullscreen API

    As we move toward more true web applications, our JavaScript APIs are doing their best to keep up.  One very simple but useful new JavaScript API is the Fullscreen API.  The Fullscreen API provides a programmatic way to request fullscreen display from the user, and exit...

  • By
    Fancy Navigation with MooTools JavaScript

    Navigation menus are traditionally boring, right? Most of the time the navigation menu consists of some imagery with a corresponding mouseover image. Where's the originality? I've created a fancy navigation menu that highlights navigation items and creates a chain effect. The XHTML Just some simple...

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!