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.

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Chapter 4: Primitive Datatypes

You may encounter the deprecated Flash 4 string concatenation operators & and add

when examining legacy code. The

+ operator should be used in Flash 5 and later. See

Appendix C for more information on backward compatibility.

The concat() function

The concat() function appends characters to a string, similar to +=. Because concat()

is a function, it uses the dot operator, like this:

var product = "Macromedia".concat(" Flash");

var sentence = "How are you";

var question = sentence.concat("?")

Take heed, though—unlike +=, the concat() function does not alter the string that it

is applied to; it merely returns the concatenated string value. In order to make use of

that value, we must assign it to a variable or other data container. Study the follow-

ing code closely, so you’ll understand the difference between

+= and concat():

// Here we mistakenly forget to store the return of concat( ) in a variable.

var userName = "Karsten";

var greeting = "Welcome to GreatSite.com";

greeting.concat(userName);

trace(greeting); // Displays "Welcome to GreatSite.com"

// The value of greeting was unaffected by concat( )

// Here we properly store the return of concat( ) in a variable.

finalGreeting = greeting.concat(" " + userName);

The concat( ) function also accepts multiple