js-proposal-algebraic-effects VS observable

I have to admit: you're perfectly right here. React of course always relied on mutable state in it's implementation – just so we don't have to. I derailed a lot here to keep this funny thread going ;) I'm still not with you on your definition of "functional", since you treated it synonymously with "purely functional". Functional means just made by applying and composing functions, and react UI is created exactly like that. There is an awesome algebraic effects proposal[1], which will hopefully will be added to JavaScript one day, then react will make use of it to become purely functional.

1: https://github.com/macabeus/js-proposal-algebraic-effects

Super interesting, there is a proposal to add this to JavaScript and several languages that use this, unison, koka & eff. I had no idea this was even a thing!

Ok I was wrongly assuming that panic was expecting an error type, in fact it's an interface{}.

> Your use of exceptions for flow control (i.e. goto) is considered harmful

Exceptions are a way to delegate error handling to the caller by giving them informations about the unexpected behavior. It implies that the expected behavior is the "happy path" (everything went well) and any deviations (errors) is unexpected.

This is far from a goto because you can have `try/finally` blocks without catch (or defer in golang).

Also, exceptions are just a kind of algebraic effects that do not resume. There was a proposal to JS for this: https://github.com/macabeus/js-proposal-algebraic-effects

This is also easier to test. assertRaises(ErrorType, func() { code... })

Almost every Go library I've seen just return an error (which is just a string), you'd need to parse it to assert that the correct error is returned in special conditions.

> especially since Observables have been widely available and actively worked on for a long time, without seeing wide adoption

Take a look at "Userland libraries" section [0] of the proposal (almost certainly written by Ben). He argues that observables get reinvented in the userland in various libraries over and over again. It is a primitive, like a Promise, only better.

[0] - https://github.com/WICG/observable?tab=readme-ov-file#userla...

Perhaps this falls into the repetitive boilerplate category you referred to, but if you want framework-agnostic domain objects that still work well with Svelte, create your own using the observer pattern.

Create an object with a subscribe method and whatever other methods make sense for updating its state. Svelte will treat it like one of its stores, and it will work with the $ syntax. It can be used with React via its `useSyncExternalStore` hook. It can be used with SolidJS via its `from` utility.

If you don't want to handle the set-up boilerplate, you could use another library like Effector or RxJS, but of course, that means another dependency. There is a gradual move to make something like this a part of the platform[1], but who knows when or if it will land.

[1] https://github.com/domfarolino/observable