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.

Further ActionScript Concepts

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less work than the nonfunction version of our code shown earlier. Enclosing reus-

able code within functions save us time and reduces the number of lines of code

needed. It also makes our code much more legible and modular. Someone reading

the code can probably guess what the area( ) function does, based solely on its name.

Don’t fret if you have questions about this function example; we’ll learn more about

functions in Chapter 9. For now, just remember that functions give us an extremely

powerful way to create complex systems. Functions help us reuse our code and pack-

age its functionality, extending the limits of what is practical to build.

Built-in functions

Notice that functions take arguments just as the trace() command does. Invoking

the function area(4, 5); looks very much the same as issuing the trace() command

such as trace (x); except that the area( ) function requires two arguments, which are

separated by commas, whereas the trace() command requires a single argument. The

similarity is not a coincidence. As we learned earlier, many Actions, including the

trace() Action, are actually functions. But they are a special type of function that is

built into ActionScript (as opposed to user-defined functions, like our area() func-

tion). It is,