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.

The ActionScript Statements

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149

Function calls are the most powerful type of expression statement. Even if a function

doesn’t return a useful value, it may have a very useful side effect. For example,

gotoAndStop() returns the value

undefined but has an important side effect—it moves

the playhead to another frame:

gotoAndStop(5); // The value of _currentframe is changed to 5.

We’ll learn more about function calls in Chapter 9 under “Running Functions.”

The var Statement

The var statement declares a new variable:

var x;

You can assign the new variable’s initial value as part of a var statement:

var x = 10;

When used outside a function, the var statement creates a variable scoped to the

timeline containing the statement. When used inside a function, the var statement

creates a variable local to that function (i.e., one that dies when the function fin-

ishes). Refer back to Chapter 2 for more information on variables.

The set Statement (Set Variable)

For most variable assignments, we use an assignment expression in statement form,

like this:

x = 30;

This kind of expression, however, requires us to know the name of our variable in

advance. If we want to generate the name of a variable dynamically during an assign-

ment, we can use the set statement, which has the following syntax:

set(variable