idiomatic way to represent key-value maps in Redux store

Question

I think that most examples I've seen online, when needing to maintain a key-value map in Redux store, they seem to choose to type it as an array of key-value pairs, e.g.:

employees: [{id: 42, emp: {name: 'John Doe'}}, {id: 43, emp: {name: 'Mary Loo'}}]

... typed as:

employees: Array<{id: number, emp: {name: string}}>

However, I would think instead that the following is a tighter typing as it explicitly disallows duplicate id:

employees: Record<id, {name: string}>

Is there a reason for choosing the former over the latter? I understand that Redux does a shallow comparison but I think that when using immutability libraries both array and object structs are equally well supported.

Answer 1

Not sure why you'd say that "the usual way is to keep it as an array". A normalized lookup table of Record<SomeId, SomeItem> would definitely be the right answer here - a plain JS object where the keys are item IDs and the values are the items themselves.