Multidimensional Arrays

The question of multidimensional arrays came up in class again yesterday and I wanted to reiterate that JavaScript does not have true multidimensional arrays. Let's (literally) take a page from the experts, here's what JavaScript: The Definitive Guide, 6th Ed, (O'Reilly Media, Inc., ISBN: 978-0-596-80552-4) has to say:

7.7. Multidimensional Arrays

JavaScript does not support true multidimensional arrays, but you can approximate them with arrays of arrays. To access a value in an array of arrays, simply use the [] operator twice. For example, suppose the variable matrix is an array of arrays of numbers. Every element in matrix[x] is an array of numbers. To access a particular number within this array, you would write matrix[x][y]. Here is a concrete example that uses a two-dimensional array as a multiplication table:

// Create a multidimensional array
var table = new Array(10);               // 10 rows of the table
for(var i = 0; i < table.length; i++)
    table[i] = new Array(10);            // Each row has 10 columns

// Initialize the array
for(var row = 0; row < table.length; row++) {
    for(col = 0; col < table[row].length; col++) {
        table[row][col] = row*col;
    }
}

// Use the multidimensional array to compute 5*7
var product = table[5][7];  // 35