Can't find this function (psuedo) 'call'

Question

a script  I have inherited uses this code for initializing and processing all the fields on a form
firstNameHelp_mc.onRelease = function() {
    _parent.fieldID = "firstName";
    _parent.setHelp();
there is no function named 'function', I wouldn't  think so anyway with reserved names etc.
is this the equivalent of declaring a function on  the fly so to speak, almost like a property get? if so what is the point?
this is a way for performing multiple actions on some thing like a release with having to create a 'real' function for each one?

Answer 1

It is one way of assigning a function to the various "on..." handlers associated with objects.  Buttons and movieclips (and objects in general) have various "on..." handlers associated with them that you can make use of by assigning functions to them.
And it is also a way you could dynamically assign a function to an object that is dynamic, such as a movieclip.  The ability to dynamically assign properties and methods to things is a handy feature, particularly when you get into working with quanitities of objects being assigned properties and methods in loops, such as setting up entire menues of buttons.
Another way you could have assigned it would have been...
firstNameHelp_mc.onRelease = functionName;
function functionName() {
    _parent.fieldID = "firstName";
    _parent.setHelp();
Which means you could have that function available to be shared by other objects or code segments as well.  So you can either have the function defined to be more globally available or specific only to a particular object.