Computed properties within a useReducer() store.

[nyenye]

Hi @kentcdodds

I followed you article in here: https://kentcdodds.com/blog/how-to-use-react-context-effectively

and it has been a huge help, but as the title says, I am kind of missing computed properties or getters. Let me give you an example:

Imagine you have an array of items, and you can select one to do stuff with it. So you could have this state on a reducer:

const state = {
  items: <Item>[],
  selectedItem: null | Item
}

which duplicates state, or you could have something like this:

const state = {
  items: <Item>[],
  selectedItemId: null | string
}

and from there derive the selectedItem in a computed property or getter of sorts, and avoid duplicating state.

Do you have any idea how this could be accomplished? Do you think it's even worth it?