Popular:
 Building Resilient Systems on AWS: Learn how to design and implement a resilient, highly available, fault-tolerant infrastructure on AWS.

JavaScript Arrays: The Difference Between [] and { }

By  on  

Using Moo 1.2 has taught me a lot about JavaScript. Of course, that means I've made a lot of mistakes but that seems to be the best way for me to learn. While browsing the Moo source, I'd always wondered the difference between arrays using brackets ([]) and braces ({}). Here's what I learned.

Use brackets for an array of simple values.

//examples
var answers = ['yes','no','maybe'];
var names = ['David','Kristina','Charlie','Angela'];

Use braces for key => value arrays and objects/properties.

//example - random array
var programmer = { 'name':'David Walsh', 'url':'https://davidwalsh.name', 'girl':'Kristina'}

//example - used for an object's properties
var Element.implement({
getText: function(){
return this.get('text');
}
});

This is similar to PHP's array system.

$arr = array('name'=>'David','position'=>'Programmer');

Have anything to add? Please share!

Request Metrics real user monitoring
Request Metrics real user monitoring
Request Metrics real user monitoring
Request Metrics real user monitoring

Recent Features

  • By
    Create a Sheen Logo Effect with CSS

    I was inspired when I first saw Addy Osmani's original ShineTime blog post.  The hover sheen effect is simple but awesome.  When I started my blog redesign, I really wanted to use a sheen effect with my logo.  Using two HTML elements and...

  • 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...

Incredible Demos

  • By
    dwProgressBar v2: Stepping and Events

    dwProgressBar was a huge hit when it debuted. For those of you who didn't catch my first post, dwProgressBar is a MooTools 1.2-based progress bar which allows for as much flexibility as possible. Every piece of dwProgressBar can be controlled by CSS...

  • By
    Chris Coyier’s Favorite CodePen Demos

    David asked me if I'd be up for a guest post picking out some of my favorite Pens from CodePen. A daunting task! There are so many! I managed to pick a few though that have blown me away over the past few months. If you...

Discussion

  1. Tim Novinger

    This is interesting. So if you use []’s in a key=>value array it just won’t work or it’s simply improper usage?

    I must admit, I’ve wondered this myself with the MOO as they seem to have pretty creative looking code conventions (that really make a lot of sense).

  2. david

    @Tim: That’s what I get from it. Please let me know if I’m wrong.

  3. Rasmus

    I feel like you’re missing one of the finer points in this bracket/brace post; braces define Objects – not Arrays!

    The following are essentially the same:

    var myArray = [];
var myArray = new Array();

    … as are:

    var myObject = {};
var myObject = new Object();

    Javascript is by no means perfect – so you’ll have to know the pitfalls, like erroneously mixing keys and indexes in an Array (like you can do in PHP – bad).
    As javascript doesn’t have associative arrays Objects are the closest thing.

    • Kyle

      Ahh!! I am so enlightened by that! Thank you! That makes so much sense now! Too many exclamations!! I need to stop but can’t!

      On a serious note, that does clarify a few questions I had.

  4. Mantasha Zaara

    Thanks David

    U solved my problem. I am first time using Javascript in my website and i was getting one problem with one line. 

     mycarousel_itemList[counter]=  
[{url: "ID,'thumbnail', true); ?>",link: "",title: ""}]
;

    and u solved it … thanks again…regards

  5. RD

    Thanks Rasmus. This is what Exactly i was looking for.

  6. Richard

    I’m not new to JavaScript but trying to move forward, what seems to be a mistery to me is the use of punctuation ( ‘.,’:([{‘ )???. and the rules they surely must adhere too. Not one tutorial (and I have explored a lot) explains what these things actually mean and where they are to be used. It almost seems arbitrary, like learning the bizarre ‘illogical’ rules of a spoken language. Can yo help?

    Regards,
    Richard.

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