Creating arrays in Javascript

Question

I am little new to javascript and I am having alittle trouble wrapping my head around making a 2d (or maybe i might need a 3d) array in javascript.

I currently have 2 pieces of information i need to collect: an ID and a value so I created the following:

var myArray = [];

var id = 12;
var value = 44;

myArray[id]=value;

But I realized that this is not easy to loop through the array like a for loop so i was thinking of this:

myArray[myArray.length] = id;
myArray[myArray.length-1][id]=value;

I wanted to do this so that in a for loop i could get the ids and the values easily but the above only returns the value when i loop through it. Any suggestions on how to get this working or is there a better way to do this?

Thanks

I'm confused about what you're trying to do. Are you trying to store a bunch of (id, value) pairs? Do you need to retrieve the value by id at a later time or just iterate through the pairs? — takteek
– takteek, Commented Mar 3, 2012 at 4:49
@takteek iterate through the pairs so I want to access both the value and id at element 0 — user1219627
– user1219627, Commented Mar 3, 2012 at 4:57

rjz · Accepted Answer · 2012-03-03 04:50:57Z

19

Why not use an array of object hashes? This approach allows you to store multiple values in a key:value format:

var myArray = [];
var myElement = {
  id: 12,
  value: 44
}

myArray[0] = myElement;

You could then loop through all of the elements in myArray like so:

var i = 0,
    el;

while (el = myArray[i++]) {
  alert(el.id + '=' + el.value);
}

answered Mar 3, 2012 at 4:50

rjz

16.5k3 gold badges39 silver badges35 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

user1219627 Over a year ago

id and value are not always 12 and 44, its whatever the user sets the var to unless theres a way to set myElement.id = 0 myElement.value then set array to myElement

takteek Over a year ago

You just described how to do it, haha. myElement.id = 0

user1219627 Over a year ago

@takteek Awesome thanks...I was hoping it would work the same way

snjoetw · Accepted Answer · 2012-03-03 05:10:51Z

3

I think what you want is a dictionary like structure (in JS it's called an object), eg { id => value}

In JS you can do something like this:

var myDict = { 'myId' : 'myValue' };
myDict[12] = 44; // from your example and this will be added to myDict
myDict[11] = 54;

for (var key in myDict) {
  console.log('key: ' + key + ', value: ' + myDict[key]);
}

The output will be:

key: 11, value: 54

key: 12, value: 44

key: myId, value: myValue

answered Mar 3, 2012 at 5:10

snjoetw

4092 silver badges7 bronze badges

Comments

Victor · Accepted Answer · 2012-03-03 05:08:53Z

Probably the best way to do multi-dimensional arrays is creating then on the fly using loops.

so you can have like array[x][y][z] like I saw your 3D-array tag.

To loop trough is not that hard, you can verify the length of the array, when you reach the end of one dimension e.g. z increase the y by one and reset z to 0.

Exemple constructor of 2d-array:

function Array2d(x,y){

    var array = new Array(x);

    while(x>0){
        array[x]=new Array(y);
        x--;
    }

    return array;
}

to create a 2d array you can use like this:

var myMatrix = Array2d(4,4);

this is generate a empty 4x4 matrix myMatrix[4][4]

(0,0) (1,0) (2,0) (3,0)
(0,1) (1,1) (2,1) (3,1)
(0,2) (1,2) (2,2) (3,2)
(0,3) (1,3) (2,3) (3,3)

to do a 3D or more dimensions just put other loop inside the loop.

note: I not tested this function, this is just a algorithm, you should verify the input, if you insert a negative length or float this is probably crash you browser.

Usama Yazdani · Accepted Answer · 2024-06-27 19:02:53Z

0

There is no Associative array in javascript. so if you name a index as named it will be converted as object

so you can create like

var arrayToBe = [];
arrayToBe[]="test";

this way you can add values to that array

answered Jun 27, 2024 at 19:02

Usama Yazdani

111 bronze badge

Comments

Fabio RIZZI · Accepted Answer · 2024-11-18 15:01:39Z

0

object in js are more powerful

You can do something like that :

let myArray = [];
myArray.push(
{ id: 1210312, value: 12 }
);

If you want to log each item from this array, you can use this to show in the console each item of your array !

for (let item of myArray) {
    console.log(`id: ${item.id}, value: ${item.value}`);
}

answered Nov 18, 2024 at 15:01

Fabio RIZZI

1

Collectives™ on Stack Overflow

Creating arrays in Javascript

5 Answers 5

3 Comments

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

3 Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related