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.

Running Functions

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183

Function scope

Determining the availability and life span of a function, and the accessibility of

variables referenced in a function body.

Let’s get to it!

Creating Functions

To make a basic function we specify a function name and a block of statements to

perform, like this:

function funcName (param1, param2,...paramn) {

statements

}

The function keyword starts the declaration of our new function. Next comes our

function name,

funcName, which we’ll use later to invoke our function. The specified

funcName must be a legal identifier

*

, but otherwise it can be any unique name we

choose (avoid creating functions with the same name as built-in functions). Next, we

supply a pair of parentheses,

(), that enclose any parameters (param1, param2, etc.),

separated by commas, which we’ll discuss later. If our function does not have any

parameters, we include the parentheses but leave them empty. Finally, we provide

the function body (i.e., statement block), which contains the code that’s executed

when our function is called.

Let’s make a very simple function:

1. Create a new empty Flash movie.

2. On frame 1 of Layer 1 of the main movie timeline, attach the following code:

function sayHi () {

trace("Hi there!");

}

That was easy—we’ve just created a function named sayHi(). This simple