Javascript defining array. "arrayception"

Question

I am trying to create a list of "items" in a canvas game. For example, an array named list. Each element must contain the information about each item. First element will contain something different. I will remove first one with 'shift()' command. Like :

list.shift(); 
list[0]['name']
list[0]['id']
list[0]['x']
list[0]['y']
list[1]['name']
list[1]['id']
list[1]['x']
list[1]['y']

but i don't know how to define something like this. normally i define arrays like

{"name" : xx, "id" : 5 ... }

but this works like :

list['name']
list['id']

{ ... } is not an array, it's an object (literal).

user395760
– user395760

2012-03-10 08:32:13 +00:00
Commented Mar 10, 2012 at 8:32 — user395760
– user395760, Commented Mar 10, 2012 at 8:32

KooiInc · Accepted Answer · 2012-03-10 08:55:48Z

2

use:

var list = [];
list[0] = {name: 'xx', id: 0, /*etc*/};
list[1] = {name: 'yy', id: 1, /*etc*/};

it creates an array of objects. You can use it like this:

var first = list.shift();
first.name; //=> xx
//or
var first = list[0];
first.name; //=> xx

Note: using {...} (Object literal) creates an Object, not an Array. An array can be created using an Array literal: [...]. Although an object is sometimes said to be an Associative Array, it is not an Array object, so things like {...}.shift() will not work for Objects.

edited Mar 10, 2012 at 8:55

answered Mar 10, 2012 at 8:34

KooiInc

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4 Comments

deniz Over a year ago

how can i send this through websockets using JSON.stringify ?

Arend Over a year ago

You can just serialize the list object

KooiInc Over a year ago

for the example of my answer: var liststr = JSON.stringify(list) returns "[{"name":"xx","id":0},{"name":"yy","id":1}]", var list2 = JSON.parse(liststr) converts the string back to the array of obects. The string can be sent through websockets I suppose, that's out of the realm of this question.

deniz Over a year ago

thanks for the answer. i will look through it a bit. by the way i have learnt that [] is array, {} is object. thanks. so i will define objects in [] and send that.

mpm · Accepted Answer · 2012-03-10 08:43:25Z

1

There are no associative arrays in javascript. so for instance , when you do

var _array = []
_array["field1"] ="value";

you are actually adding a property to the _array object .

_array.field1 = value <=> _array["field1"] ="value";

so if you want to create a collection of objects , do

var collection =[];
var myObject = {"field1":"value1"};
collection.push(myObject);

answered Mar 10, 2012 at 8:43

mpm

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