creating multi-dim arrays (JS)

Question

I was trying to create a 3-dimensional array and couldn't find an easy way to do it.

array = [[[]]];

or

array = [][][];

or

array = []; array[] = []; array[][] = [];

would for example not work. (the console'd say the second array is 'undefined' and not an object, or for the second and third example give a parse error).

I cannot hard-code the information either, as I have no idea what the indexes and contents of the array are going to be (they are created 'on the fly' and depending on the input of a user. eg the first array might have the index 4192). I may have to create every array before assigning them, but it would be so much easier and faster if there's an easier way to define 3-dimensional arrays. (there'll be about 2 arrays, 25 subarrays and 800 subsubarrays total) every millisecond saves a life, so to say.

help please?

score 3 · Accepted Answer · 2013-05-24 20:05:09Z

3

JavaScript is dynamically typed. Just store arrays in an array.

function loadRow() {
    return [1, 2, 3];
}

var array = [];
array.push(loadRow());
array.push(loadRow());
console.log(array[1][2]); // prints 3

edited May 24, 2013 at 20:05

answered May 24, 2013 at 15:49

user142019

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Comments

pgreen2 · Accepted Answer · 2013-05-24 20:01:17Z

1

Since arrays in javascript aren't true arrays, there isn't really a multidimensional array. In javascript, you just have an arrays within an array. You can define the array statically like this:

var a = [
 [1,2,3],
 [4,5,6],
 [7,8,9]
];

Or dynamically like this:

var d = [];
var d_length = 10;
for (var i = 0;i<d_length;i++) {
  d[i] = [];
}

UPDATE

You could also use some helper functions:

function ensureDimensions(arr,i,j,k) {
  if(!arr[i]) {
    arr[i] = [];
  }
  if(!arr[i][j]) {
    arr[i][j] = [];
  } 
}

function getValue(arr,i,j,k) {
  ensureDimensions(i,j,k);
  return arr[i][j][k];
}

function setValue(arr,newVal,i,j,k) {
  ensureDimensions(i,j,k);
  arr[i][j][k] = newVal;
}

edited May 24, 2013 at 20:01

answered May 24, 2013 at 15:53

pgreen2

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1 Comment

user1916542 Over a year ago

thanks, but as I mentioned I don't know what will be in the arrays or how long they will be.. this approach will sadly not help me.

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