Make a Notes client JavaScript User Guide

I'd like to know the details of how to use JavaScript in a form in the Notes client (V11+). One can do marvellous things in the UI, but most of it is unknown to the average developer. Could you please write a User's Guide, describing what javaScript is possible/supported? We know it's v1.3, and documentation on the language itself is available, but there's nothing on the specifics of the JavaScript methods themselves.

As an example: I know that document.forms[] and window.timeout() are available in the Notes client, but document.getElementById() isn't.

Documentation, Maestros, please!