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

Incredible Demos

  • By
    Sexy Opacity Animation with MooTools or jQuery

    A big part of the sexiness that is Apple software is Apple's use of opacity. Like seemingly every other Apple user interface technique, it needs to be ported to the web (</fanboy>). I've put together an example of a sexy opacity animation technique...

  • By
    CSS Columns

    One major gripe that we've always had about CSS is that creating layouts seems to be more difficult than it should be. We have, of course, adapted and mastered the techniques for creating layouts, but there's no shaking the feeling that there should be a...

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!