ActionScript for Flash MX: The Definitive Guide, Second Edition

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

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Chapter 5: Operators

if (xPos < 0 || xPos > 100) {

trace ("xPos is not between 0 and 100 inclusive.");

}

Note that the variable xPos must be included in each comparison. The following

code shows a common mistaken attempt to check

xPos’s value twice:

// Oops! Forgot xPos in the comparison with 100

if (xPos < 0 || > 100) {

trace ("xPos is not between 0 and 100 inclusive.");

}

Logical AND

Like the logical OR operator, logical AND is used primarily to execute a block of

code conditionally—in this case, only when both of two conditions are met. The log-

ical AND operator takes the general form:

operand1 && operand2

Both operand1 and operand2 can be any valid expression. In the simplest case, in

which both operands are Boolean expressions, logical AND returns

false if either

operand is

false and returns true only if both operands are true. In summary:

true && false // false because second operand is false

false && true // false because first operand is false

true && true // true because both operands are true

false && false // false because both operands are false (either is sufficient)

Let’s see how the logical AND operator is used in two examples. In Example 5-4, we

execute a trace() statement only when two variables are both greater than 50.

Because the expressions x>50 and y>50 are both

true ...