ActionScript for Flash MX: The Definitive Guide, Second Edition

This is the Title of the Book, eMatter Edition

Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

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Chapter 4: Primitive Datatypes

The eval() function was used frequently in Flash 4 to generate variables dynamically

because support for arrays wasn’t available until Flash 5. Such uses of eval() should

be rewritten using arrays when upgrading legacy code.

The Boolean Type

Boolean data is used to represent the logical states of truth and falsehood. Hence

there are only two legal values of the boolean datatype:

true and false. Notice that

there are no quotation marks around the words

true and false because Boolean data

is not string data. The keywords true and false are reserved primitive data values

and cannot be used as variable names or identifiers.

We use Boolean values with conditional expressions to add logic to the execution of

code. For example, we might assign the value

true to a variable that tracks the status

of a spaceship’s firepower:

shipHasDoubleShots = true;

By comparing shipHasDoubleShots to the Boolean literal true, we can decide how

much damage to inflict when a shot hits its target:

if (shipHasDoubleShots = = true) {

// Shoot them with twice the power.

// This will be reached if the comparison is true.

} else {

// Shoot them with a single dose.

// This will be reached if the comparison is false.

}

When the double-shot power runs out, we can set the variable to false