React and friends made themself show up on every party. Even if the model isn't remotely appropriate for the taks at hand, you have to argue about them. I am convinced that half the modern frontend devs don't even know how a "classic" web app could work. SPAs or frameworks usually used for SPAs are the default state and there isnn't any competitive option with a real name except jquery/ajax/html. Even talking about the latter will brand you as dinosaur in many circles.

> but I wonder how difficult it is.

Its not if you have some basic understanding how the code actually works.

> but I find it a bit hard to imagine doing an actual app with vanilla JS.

Try it. It will blow your mind how simple it is and how little overhead it requires.

I went from developing simple server-rendered websites enhanced with a bit jQuery straight to React-style JS.

I'm interested in studying the source of less or more complex JS-apps, that were developed without SPA-Frameworks.

One I'd like to see would be Construct3, but alas it's not open-source.

I'd very much appreciate links and hints!

You can look at my SPA that maintains state perfectly well and persistently without any framework. It isn't hard, but you would have to be willing to write original code.

https://prettydiff.com/

All of the UI is defined here: https://github.com/prettydiff/prettydiff/blob/master/api/pre...