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

Primitive Datatype Equality

For the primitive datatypes, the result of most equality tests is fairly intuitive.

Table 5-2 lists the rules that govern equality for each primitive datatype.

Composite Datatype Equality

As shown in “Copying, Comparing, and Passing Data” in Chapter 3, variables con-

taining composite data (objects, arrays, functions, or movie clips) store references to

the data and not the data itself; hence, it is possible for two variables to refer to the

same underlying item. Two such operands are considered equal if and only if they

refer to the same underlying composite datum, not if the operands refer to two differ-

ent items that contain identical contents. Even if two operands can be converted to

the same primitive value, they are not necessarily considered equal.

The following examples illustrate how ActionScript compares the references that

point to the composite data, not the data itself. In the first example, the operands

(

nameList1 and nameList2) refer to arrays that have the same elements but are actually

Table 5-2. Equality of primitive datatypes

Type Terms of equality (both operands must be of given type)

Number If

operand1 is the same number as operand2, the result is true. If both operands are

+Infinity or both are –Infinity, the result ...