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 Ways that CSS and JavaScript Interact That You May Not Know About

    CSS and JavaScript:  the lines seemingly get blurred by each browser release.  They have always done a very different job but in the end they are both front-end technologies so they need do need to work closely.  We have our .js files and our .css, but...

  • By
    LightFace:  Facebook Lightbox for MooTools

    One of the web components I've always loved has been Facebook's modal dialog.  This "lightbox" isn't like others:  no dark overlay, no obnoxious animating to size, and it doesn't try to do "too much."  With Facebook's dialog in mind, I've created LightFace:  a Facebook lightbox...

Incredible Demos

  • By
    CSS Vertical Centering

    Front-end developing is beautiful, and it's getting prettier by the day. Nowadays we got so many concepts, methodologies, good practices and whatnot to make our work stand out from the rest. Javascript (along with its countless third party libraries) and CSS have grown so big, helping...

  • By
    Image Manipulation with PHP and the GD Library

    Yeah, I'm a Photoshop wizard. I rock the selection tool. I crop like a farmer. I dominate the bucket tool. Hell, I even went as far as wielding the wizard wand selection tool once. ...OK I'm rubbish when it comes to Photoshop.

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!