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.

202

|

Chapter 9: Functions

Obviously we can count down without using recursive anonymous functions. We’ll

see a more realistic example of function recursion in the section on “Recursive Func-

tions” later in this chapter. Using

arguments.callee to refer to the current function

(rather than the function’s actual name) alleviates the need to update our code if the

function’s name changes.

We can use

arguments.caller to execute or identify a calling function, as described

in the Language Reference.

Passing Parameters by Value Versus by Reference

There’s one more parameter subtlety we should consider—the difference between

passing data to a function by value and by reference.

When we pass a primitive data value as an argument to a function, the function

receives a copy of the data, not the original. Changes made to a parameter in the

function have no effect on the original argument outside that function. In

Example 9-5,

variableName’s value is initially set to 25. Changing its value to 10

within the setValue() function has no effect on

y’s value.

Primitive data is therefore said to be passed by value. When we pass composite data

as an argument to a function, however, the function receives a reference that points

to the same data as the original argument, not just a duplicate of the data. Altering ...