Defining a function

Functions, like variables, 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 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 (x) {
   return (x*2)+3;
}

To define a Timeline function, use the function action 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) {
  return Math.PI * radius * radius;
}

You can also define a function by creating a function literal—an unnamed function that is declared in an expression instead of in a statement. You can use a function literal to define a function, return its value, and assign it to a variable in one expression, as shown in the following example:

area = (function() {return Math.PI * radius *radius;})(5);

When a function is redefined, the new definition replaces the old definition.