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.

The Equality and Inequality Operators

|

121

The Equality and Inequality Operators

We use the equality operator (==) to test whether two expressions have the same

value. An equality test takes the general form:

operand1 = = operand2

where operand1 and operand2 can be any valid expression. The equality operator can

compare operands of any type. When

operand1 and operand2 are equal, the expres-

sion returns the Boolean value

true; when they differ, it returns the Boolean value

false. For example:

// Store the value 2 in x.

var x = 2;

// Is x equal to 1?

if (x = = 1) {

// false; nothing is displayed

trace("x is equal to 1);

}

// Is x equal to 2?

if (x = = 2) {

// true; message is displayed

trace("x is equal to 2);

}

The equality operator is created using two equals signs in a row (==). It

determines whether two expressions are equal, and it should not be

confused with the assignment operator (

=), which is a single equals

sign used to assign a new value to a variable. Flash MX also supports

the strict equality operator, created using three equals signs (

===). See

the “The Strict Equality and Inequality Operators” later in this chapter.

Consider this example:

if (x = 5) {

trace("x is equal to 5")

}

This example does not check whether x equals 5. Instead, it sets x equal to 5. It then

evaluates the variable ...