Call JavaScript or be called by JavaScript

1. Calling Flex methods in JavaScript
In Flex, you can use ExternalInterface to call Flex methods by adding specified public methods to the list of callable methods in the Flex application. A method can be added to this list by calling addCallback() in a Flex application. addCallback registers an ActionScript method as a method that JavaScript and VBScript can call. The definition of the
addCallback() function is as follows:
addCallback(function_name:String, closure:Function):void The
function_name parameter is the method name called by the script in the Html page. The closure parameter is the local method to be called. This parameter can be a method or an object instance.

For example:

import flash.external.*;
public function myFunc():Number {
return 42;
}
public function initApp():void {
ExternalInterface.addCallback ( "myFlexFunction",myFunc);
}

Then in the Html page, first get the reference to the SWF object, that is, the Id attribute of the Swf declared with