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

viewVars(10); // In Flash Player 6, displays:

// x is 10

// y is undefined

// z is undefined

// (In Flash Player 5, undefined variables are displayed as a

// blank string in the Output window.)

When a function is called with more parameters than the declared number, excess

parameter values can be accessed using the arguments object. (Obviously, the excess

parameters can’t be accessed by name, as explicitly declared parameters can, because

their names were not declared.)

The arguments Object

During the execution of any function, the built-in arguments object gives us access to

the following:

• The number of parameters that were passed to the function

• An array containing each of those parameter values

• A reference to the function being executed

• A reference to the calling function, if any

The arguments object is really a special hybrid between an array and an object with

some other properties. In Flash 5, arguments was not an array instance. In Flash MX,

however, arguments is an instance of the Array class and therefore supports Array’s

methods and properties.

Retrieving parameter values from the arguments array

The arguments array lets us check the value of any function invocation argument,

whether or not that parameter is defined formally in the function’s