Javascript multi-dimension array initialization

Question

I'm looking for the best way to initialize multi-dimensional arrays in Javascript. I'm much more familiar with PHP where I'm not obliged to declare arrays or dimensions before feeding it with values.

Basically what I tried to do is create an array with the following format

catalogue[i]["name"]="a name";
catalogue[i]["description"]="a description";

...etc...

If I do the following:

var catalogue = new Array();
for (i=0; i<otherarray.length;i++)
    {
       catalogue[i]['name']=otherarray[i];
    }

Catalogue is undefined, I also tried with catalogue[i].name but same issue. If I only assign a simple value like catalogue[i]=2, it works but that's not what I'm looking for. I couldn't find a working example of what I'm looking for.

Do I need to initialize every possible dimension of an array before being able to feed it with new values?

Thanks Laurent

Note that arrays don't have keys in javascript, only numeric indexes, so what you really want to create is an object. — adeneo
– adeneo, Commented Dec 28, 2015 at 16:23
catalogue isn’t undefined, catalogue[i] is. You can sill write catalogue[i] = {}; right before catalogue[i]['name'] = otherarray[i];. — Sebastian Simon
– Sebastian Simon, Commented Dec 28, 2015 at 16:24

void · Accepted Answer · 2015-12-28 16:24:26Z

2

var catalogue = new Array();
for (i = 0; i < otherarray.length; i++) {
  catalogue[i] = {};
  catalogue[i]['name'] = otherarray[i];
}

Or

var catalogue = new Array();
for (i = 0; i < otherarray.length; i++) {
  catalogue.push({"name":otherarray[i]});
}

answered Dec 28, 2015 at 16:24

void

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Aᴍɪʀ · Accepted Answer · 2015-12-28 16:30:33Z

1

Put this in your loop to create the object you want to store the values in:

catalogue[i] = {}; OR catalogue.push({});

Your code would be like this then:

var catalogue = new Array();
for (i=0; i<otherarray.length;i++)
{
   catalogue[i] = {}; // initialization
   catalogue[i]['name']=otherarray[i];
}

Note that you can initialize and assign a value in the same line:

var catalogue = new Array();
for (i=0; i<otherarray.length;i++)
{
    catalogue[i] = {
        name: otherarray[i],
        otherKey: 'otherValue' // list all of your keys and values
    };
}

edited Dec 28, 2015 at 16:30

answered Dec 28, 2015 at 16:24

Aᴍɪʀ

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1 Comment

Laurent Over a year ago

That's exactly what I was looking for, thanks a lot!

Mouradif · Accepted Answer · 2015-12-28 16:32:39Z

1

If you want string keys in your array in Javascript you have to declare an Object. The catalogue variable itself is an array but each element inside that array is an object with the two keys "name" and "description". For example this code works :

var c = [1,2,3,4,5];
var n = ['one', 'two', 'three', 'four', 'five'];
var cat = [];
for (i = 0; i < c.length; i++)
{
  cat[i] = {
    name : n[i],
    value: c[i]
  };
}

now if you console.dir(cat); it outputs this result :

Array[5]
    -> 0 : Object
        name: "one"
        value: 1
    -> 1 : Object
        name: "two"
        value: 2
    ...

answered Dec 28, 2015 at 16:32

Mouradif

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