Multidimensional array in Javascript

I’m trying to get a multidimensional array working. I have:

// Global variable grid of Cards (Cards is my own class)
var aGrid : Cards[,];

function Start(){
    // Init aGrid
    for( var i = 0; i < 4; ++i ){
        for( var j = 0; i < 4; ++i ){
            aGrid[ i, j ] = new Card();
        }
    }
}

function accessGrid(){
    // Try to access initialized aGrid
    // This bombs, saying aGrid is a null value
    var card : Card = aGrid[ intX, intY ];
}

When I run the app, the accessing of aGrid fails saying aGrid is null, even though the intX and intY indexing variables are valid (i.e., are values between 0<4).

Didn’t I initialize aGrid correctly in the Start() function? Do I need some type of aGrid = new Card[4,4]; statement?

Actually, while writing the original question, I came up with the correct answer. I added the statement:

aGrid = new Card[ 4, 4 ];

to the Start() function and everything works.