ActionScript for Flash MX: The Definitive Guide, Second Edition

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Referencing Array Elements

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Referencing Array Elements

Once we’ve created an array, we’ll inevitably want to retrieve or change the value of

its elements. To do so, we can use the array access operator (i.e., square brackets),

[],

which we introduced in Chapter 5.

Retrieving an Element’s Value

To access an individual element, specify the array’s identifier, followed by the ele-

ment’s index within square brackets, like this:

arrayName[elementNumber]

where arrayName is usually a variable pointing to the array, and elementNumber is an

integer value specifying the element’s index. The first element is number 0, and the

last element number is 1 less than the array’s length. Specifying an element number

greater than the last valid element number causes the interpreter to return

undefined.

For example:

// Create an array using an array literal, and store it in trees

var trees = ["birch", "maple", "oak", "cedar"];

// Display the first element of trees in the Output window

trace(trees[0]); // Displays: "birch"

// Assign the third element's value to the variable favoriteTree

// (remember indexes start at 0, so index 2 is the third element!)

var favoriteTree = trees[2]; // favoriteTree becomes "oak"

Now here’s the fun part. Since we can specify the index of an element as any num-

ber-yielding expression, ...