The simplest type of multidimensional array is a two-dimensional
array, in which elements are organized conceptually into a grid of
rows and columns -- the rows are the first dimension of the array,
and the columns are the second.

Let's consider how a two-dimensional array works with a
practical example. Suppose we're processing an order that
contains three products, each with a quantity and a price. We want to
simulate a spreadsheet with three rows (one for each product) and two
columns (one for the quantity and one for the price). We create a
separate array for each row, treating the elements as columns:

var row1 = [6, 2.99]; // Quantity 6, Price 2.99
var row2 = [4, 9.99]; // Quantity 4, Price 9.99
var row3 = [1, 59.99]; // Quantity 1, Price 59.99

Next, we place the rows into a container array named
`spreadsheet`:

var spreadsheet = [row1, row2, row3];

Now we can find the total cost of the order by multiplying the
quantity and price of each row and adding them all together. We
access a two-dimensional array's elements using two indexes
(one for the row and one for the column). The expression
`spreadsheet[0]`, for example, represents the first
row's two-column array. Hence, to access the second column in
the first row of `spreadsheet`, we use
`spreadsheet[0][1]`:

// Create a variable to store the total cost of the order
var total;
// Now find the cost of the order. For each row, multiply the columns
// together, and add that to the total.
for (var i = 0; i < spreadsheet.length; i++) {
total += spreadsheet[i][0] * spreadsheet[i][1];
}
trace(total); // Displays: 117.89

Aside from storage and access, multidimensional arrays behave just
like normal arrays. We may happily use all of the
*Array* methods to manipulate data stored in
multidimensional arrays.

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11.9. General Array-Manipulation Tools | | 11.11. The Multiple-Choice Quiz, Take 3 |