Flash CS3 Documentation

Learning ActionScript 2.0 in Adobe Flash > Functions and Methods > About functions and methods > Defining global and timeline functions

Defining global and timeline functions

In About functions and methods, you explored the different kinds of functions that are available in Flash. As with variables, functions are attached to the timeline of the movie clip that defines them, and you must use a target path to call them. As with variables, you can use the _global identifier to declare a global function that is available to all timelines and scopes without using a target path. To define a global function, precede the function name with the identifier _global, as shown in the following example:

_global.myFunction = function(myNum:Number):Number {
   return (myNum * 2) + 3;
};
trace(myFunction(5)) // 13

For information on _global and scope, About variables and scope.

To define a timeline function, use the function statement followed by the name of the function, any parameters to be passed to the function, and the ActionScript statements that indicate what the function does.

The following example is a function named areaOfCircle with the parameter radius:

function areaOfCircle(radius:Number):Number {
  return (Math.PI * radius * radius);
}
trace(areaOfCircle(8));

You can also define functions in numerous other ways. For more information on each kind of function, see the following sections:

• About built-in and top-level functions
• Writing named functions
• Writing anonymous and callback functions
• About function literals
• About constructor functions
• Targeting and calling user-defined functions

For information on naming functions, see Naming functions. For a detailed example of using functions in an external class file, see Using functions in Flash and Classes.

Flash CS3