Are there such things as dynamic-dimensional arrays in JavaScript?

Question

What I mean by dynamic-dimensional arrays is multidimensional arrays that can have various dimensions. I need to create a function that does something to elements of multidimensional arrays, regardless of their dimensions. I wrote a function that should loop through all elements of a multidimensional array, but I can't find a way to get them. Here's what I wrote:

function loopThrough (multiArray, dimensions) {

  var i, indexes = new Array(dimensions.length);
  // stores the current position in multiArray as index combination

  for (i in indexes) indexes[i] = 0; // position is initialised with [0, 0, ... 0]

  while (i >= 0) {

    doStuff(multiArray[indexes[0], indexes[1], ... indexes[?]]); // this is where I got stuck

    for (i = indexes.length - 1; i >= 0 && ++indexes[i] >= dimensions[i]; indexes[i--] = 0);
    // creates the next index combination

  }

}

I also need a way to create such arrays. Say in an object's constructor, like:

function MultiArray (dimensions) {

  this.array = [];

  // create multidimensional array

}

For example, if I want to create a 5x3x8 array I should be able to call MultiArray([5,3,8]); just the same as calling MultiArray([4,6]); for a 4x6 array, or MultiArray([7]); for a plain 7-lengthed array.

An example of dimentions?

juvian
– juvian

2014-10-07 20:55:35 +00:00
Commented Oct 7, 2014 at 20:55 — juvian
– juvian, Commented Oct 7, 2014 at 20:55
You have to use recursion

hindmost
– hindmost

2014-10-07 21:04:41 +00:00
Commented Oct 7, 2014 at 21:04 — hindmost
– hindmost, Commented Oct 7, 2014 at 21:04
@hindmost you don't have to, but that is one way.

Evan Davis
– Evan Davis

2014-10-07 22:06:42 +00:00
Commented Oct 7, 2014 at 22:06 — Evan Davis
– Evan Davis, Commented Oct 7, 2014 at 22:06

Styx · Accepted Answer · 2014-10-07 21:13:47Z

2

You can use something like this:

function MultiArray(dimensions) {
    var a = [];
    if (dimensions > 1) {
        a.push(MultiArray(dimensions -1));
    }
    return a;
}
var m = MultiArray(4);

answered Oct 7, 2014 at 21:13

Styx

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1 Comment

Bergi Over a year ago

+1, though the name might better be lowercased as it is a factory function, not a constructor.

Alin Roman · Accepted Answer · 2014-10-07 21:58:23Z

function MultiArray(dimensions) {
    this.elements = [];
    var leaf = dimensions.length == 1;
    var dimension = dimensions.shift();
    for (var i = 0; i < dimension; ++i) {
        this.elements.push(leaf ? undefined : new MultiArray(dimensions));
    }
}

MultiArray.prototype.get(indexes) {
    var leaf = indexes.length == 1;
    var index = indexes.shift();
    return leaf ? this.elements[index] : this.elements[index].get(indexes);
}

MultiArray.prototype.set(indexes, value) {
    var leaf = indexes.length == 1;
    var index = indexes.shift();
    if (leaf) {
        this.elements[index] = value;
    } else {
        this.elements[index].set(indexes, value);
    }
    return this;
}

var m = new MultiArray([4, 3, 5]);
m.set([1, 2, 4], "i'm a value in a multi dimensional array");
m.get([1, 2, 4]); // should return "i'm a value in a multi dimensional array"
m.get([2, 0, 3]); // should return undefined
m.get([0, 1]); // should return an array of 5 elements

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