Ruby => Javascript translation

Question

curious... how would you write this Ruby in JS?

Array.new(3, Array.new(3, 0))

which returns

[[0, 0, 0], [0, 0, 0], [0, 0, 0]]

i've tried a variety of things but they all seem messy. i suppose some things just can't be as clean as Ruby, but how would you approach this?

maybe i'll learn a JS trick or two ;)

EDIT It was revealed that this Ruby code does not actually create 3 arrays. It creates 1 array, that the others reference. This was not the intention. I am looking for a way to easily map a 2 dimensional array with X amount of elements, and Y amount of nested elements in JS.

Also... This is a contrived example. the intension is to be able to substitute 3 with any number. this was just an example using 3.

Answer 1

You can define it like so:

var arr = [[0, 0, 0], [0, 0, 0], [0, 0, 0]];

Essentially you're explicitly defining it. However, this array contains references to three different arrays (making a total of 4). To make it behave like ruby, you would need to create a function that mimics this behavior:

function arr(size, element) {
   var ret = [];

   for(var i = 0; i < size; i++) {
       ret.push(element);
   }

   return ret;      
}

Then you could do:

var myArray = arr(3, arr(3, 0)); //myArray contains [[0, 0, 0], [0, 0, 0], [0, 0, 0]]

This is more true to the behavior you see in ruby since each element in the array is a reference to the same array (making a total of just two arrays). You can verify this by doing myArray[0][1] = 2; and then inspecting myArray. You should see the second element in each of the arrays in myArray set to 2.

Answer 2

If you just want an empty array container, just to keep track of the length, or to assign values later on, you can do this, a bit hacky but should work:

var a = [[,,],[,,],[,,]]

a[1][1] = 'foo'
alert(a[1][1]) //foo

Answer 3

The following is valid Javascript syntax, assuming you want to create 4 arrays:

[[0, 0, 0], [0, 0, 0], [0, 0, 0]]

EDIT:

Actually your ruby code only creates TWO arrays. One array is [0,0,0] and the other array contains three references to that array. If you change array[0][2] you also change array[1][2]. Are you sure this is what you want? The equivalent javascript code would be:

var b = [0, 0, 0];
var a = [b, b, b];