Chapter 9. Functions

9.1. Creating Functions

To make a basic function we simply need a function name and a block of statements to perform, like this:

function funcName ( ) {
  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. funcName must be a legal identifier.[1] Next, we supply a pair of parentheses, ( ), that enclose any optional parameters, which we'll discuss later. If our function does not have any parameters, we leave the parentheses empty. Finally, we provide the function body (i.e., statement block), which contains the code that's executed when our function is called.

[1]See Chapter 14, "Lexical Structure", for the rules that govern legal identifiers.

Let's make a (very) simple function:

1. Start a new Flash movie.

2. On frame 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( ). When we run it, the trace( ) statement in its body will be executed. Don't close the movie you've created, we'll learn to run our function next.