• in Java, a package is a unique namespace for a group of classes
• packages conceptually contain classes like files in a folder, preventing naming conflicts
• e.g., suppose two people create global MessageDialog classes, stored in two .swfs:

_global.MessageDialog = function () {
  // ...
}

• if one .swf loads into the same Flash Player as the other .swf, the second .swf's MessageDialog overwrites the first .swf's MessageDialog
• in ActionScript, there are no packages
• but we can prevent naming conflicts by defining each class on a uniquely named object, such as:

org.moock.ui.MessageDialog = function { ... }
com.yourdomain.MessageDialog = function { ... }

• now the MessageDialog classes don't conflict!
• but what about creating the objects: org, moock, and ui?
• we could do it manually:

if (!_global.org) {
  _global.org = new Object();
}

• but it's more convenient to use a custom function, AsSetupPackage():

_global.AsSetupPackage = function (path) {
  var a = path.split('.');
  var o = _global;
  for (var i = 0; i < a.length; i++) {
    var name = a[i];
    if (o[name] == undefined) {
      o[name] = new Object( );
    }
    o = o[name];
  }
}

• usage example:

AsSetupPackage("org.moock.ui");
org.moock.ui.MessageDialog = function { ... }