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 9: Functions

Nested functions are often used to encapsulate a series of complex operations into a

single package, while preventing the outside world from gaining access to its internal

workings. For an interesting example of nested functions (sometimes called inner

functions) used to simulate Java-style private members, see:

http://www.crockford.com/javascript/private.html

Nested Function Scope

When a nested function executes, the interpreter adds the nested function’s local

scope to the scope chain of its parent function. For example, in Example 9-10 the

scope chain of showFullName( ) is:

• Global object (interpreter ends its search for variables here)

• Enclosing movie clip object (where showFullName( ) was defined)

• showFullName( ) local scope (interpreter starts its search for variables here)

And the scope chain of showFirstName( ) is

• Global object (interpreter ends its search for variables here)

• Enclosing movie clip object (where showFullName( ) was defined)

• showFullName( ) local scope

• showFirstName( ) local scope (interpreter starts its search for variables here)

The scope of the nested function is the same as its parent’s with the addition of its

own local scope. If a variable does not exist in showFirstName( )’s local scope, the

interpreter will check showFullName( ...