ActionScript for Flash MX: The Definitive Guide, Second Edition

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

The Strict Equality and Inequality Operators

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The inequality operator follows the same type conversion rules as the equality opera-

tor and always yields the opposite result, including when

NaN is used as an operand:

NaN != 7 // true

NaN != NaN // true!

In some languages, including Flash 4 ActionScript, the <> operator is used as the ine-

quality operator. Flash 4 used the deprecated

ne operator for string comparisons. In

Flash 5 and Flash MX, != should be used in lieu of

<> and ne for comparisons,

regardless of the operands’ datatypes. See also the logical NOT operator (

!) dis-

cussed later in this chapter.

Common Uses of Equality Operations

We’ll frequently use equality operations to form Boolean expressions within condi-

tional statements or to assign a Boolean value to a variable. Example 5-2 shows both

situations and demonstrates the

!= and == operators in action.

Experienced programmers will be quick to point out that we could have reduced if

(isWin = = true) to if (isWin), because

isWin holds a Boolean value, which is what the

if statement expects. While that’s quite right, it doesn’t make for a good example of

the equality operator, now does it? Furthermore, new programmers usually find the

more verbose form clearer. Both approaches are perfectly acceptable. We’ll cover this

topic ...