Javascript two dimensional arrays

I have declared a two-dimensional array, like so:

a = [[]]

However, when I try to give a second dimension value using a first dimension index other than 0, it doesn't work:

a[1][0] = "foo" //returns error

Is there a better way around this than manually defining every index you need as an array, i.e.:

a[1] = [];
a[2] = [];
a[3] = [];
//et cetera

Answer

N-Dimensional arrays do not exist in javascript - you have to just make arrays containing arrays as elements.

You're getting an error because a = [[]]; declares an array with one element, which happens to also be an array. Therefore a[0] is the internal array, but a[1] does not exist because you never declared it. The easiest way to properly declare a "two dimensional array" would be to use a loop:

var outerArray = [];
var numInternalArrays = 5;
for (var i = 0; i < numInternalArrays; i++) {
    outerArray[i] = [];
}