Just use an array of array if the memory is not the problem;

var table = [];
table.length = 10; // 10 rows;

for (var i = 0; i < array.length; i++) {
    table[i] = [];
    table[i].length = 20; // 20 columns for each row.
}

If the table is big but only a few cells are used, you can also use a hash of hash:

var table = {};
table.rowCount = 10; // there're 10 rows

table[1] = {}
table[1].columnCount = 20 // 20 cells for row 1
table[1][3] = "hello world";

// visit all cells
for (var row in table) {
    for (var column in table[row] {
        console.log(table[row][column]);
    }
}

You can even mix hash and array.