ActionScript for Flash MX: The Definitive Guide, Second Edition

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

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Chapter 9: Functions

The parentheses contain the values for any parameters required by the function. If

the function requires no parameters (as determined by the function declaration), the

parentheses are left empty. Let’s try invoking our sayHi() function, which has no

parameters, to get the hang of basic function invocation.

Here, again, is our sayHi() function declaration:

function sayHi () {

trace("Hi there!");

}

And here’s our sayHi( ) function invocation:

sayHi();

In this simple demonstration, we add the function invocation to the same script con-

taining the function declaration, but we’ll see later that this isn’t always the case.

When the sayHi( ) function call is executed, the sayHi function is invoked, so its

function body runs, causing “Hi there!” to appear in the Output window.

You can see that typing sayHi(); is more convenient than typing the whole trace()

statement, and the function name, sayHi, is a more meaningful description of what

our code does. Using thoughtful function names makes our code more readable,

almost like human sentences. In this book and in most programming documenta-

tion, function names are conventionally listed with the invocation parentheses, as in

“the sayHi( ) function” versus “the sayHi function.” This convention makes function

names easy to ...