Well done @Bill_French, you have made a pack to do what I have been doing with my non-pack process - this makes it so much easier. Itsy is based on the same library that we use at Agile-Dynamics.
Its amazing what you can do with this within Coda; however it is a display-only embed - getting data back from the js code into coda is not possible.
I have been using this technique in coda documents for my students in the CoderDojo to teach javascript (as well as HTML and CSS) - its a kind of “Codepen” inside a Coda doc.
There are limits to the size of the code you can run - since it all gets packed into the URL (using Base64) - so the amount of code you can handle is limited. We set up our own server on github to try to expand the amount of code that can be run - but failed. The rules imposed by Coda on embedded <iframe>s prevents it - and limits the process to being a display-only tool.
But making it into a Pack is a huge step forward - very grateful to you @Bill_French, well done indeed.
Max