In 2001 or so, I was building an HTML based email client. We used a hidden iframe to execute JS to load data from the server and manipulate the DOM with the result. It was not quite as neat and elegant as this—the browser support was not there. However, the basic mechanism was the same.

It warms my heart to see the basic mechanism in such a compact package, without libraries upon libraries and machinations to make things work. This is probably perfect for 90% or so use cases where react or similar FE frameworks are used at the moment.

We later used to joke that we used Ajax before Ajax was a thing.