How can I implement a non React reaction (side effect) after an atom or selector change?

[zisiszikos]

Assuming I have an Atom represanting a list like:

const myList = atom({
  key: 'myList',
  default: [],
});

and there are a few places in my code that this array changes (add or remove item).
How can I write some code like a Reaction (side effect) that runs every time this atom's array change? And I mean without using React at all (useEffect, useCallback, useRecoilCallback).

For example, MobX has reactions, redux has something like thunks or sagas.

[BenjaBobs]

You can use Atom Effects for this.

[zisiszikos]

Thanks for your answer.

I tried to make an example app that uses Atom Effects and I couldn't make it work. The problem is that I cannot get or set the value of another Atom from inside an Atom Effect function.

Consider the case where the selected item of a list must conditionally change whenever an item is removed from the list.

Here is an example code: example