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JavaScript Arrays: The Difference Between [] and { }

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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');

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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.

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