ActionScript for Flash MX: The Definitive Guide, Second Edition

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

The Equality and Inequality Operators

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two distinct arrays. The references are therefore different, and the comparison evalu-

ates to

false:

nameList1 = ["Linkovich", "Harris", "Sadler"];

nameList2 = ["Linkovich", "Harris", "Sadler"];

// The two arrays are not considered equal, so

// the trace() statement doesn't execute.

if (nameList1 = = nameList2) {

trace("They're the same");

}

In this example, cities and canadianCities both refer to the same array, so they are

equal:

canadianCities = ["Toronto","Montreal","Vancouver"];

cities = canadianCities;

// The two arrays are considered equal, so

// the trace() statement does execute.

if (cities = = canadianCities) {

trace("They're the same");

}

In this example, myFirstBall and mySecondBall have the same constructor (i.e., are

both objects derived from the same class), but they exist as separate (unequal)

instances:

function Ball ( ) {

// ...initialization code goes here...

}

myFirstBall = new Ball( );

mySecondBall = new Ball( );

myFirstBall = = mySecondBall // false

As shown in Chapter 3, composite data values are compared by reference, not by

value.

To duplicate an array’s contents without copying the array reference, we can use the

Array.slice() method. In this example, we copy the elements from the

dishes array

into

kitchenItems:

dishes = [ "cup", "plate", ...