| type Listener = () => void |
| type OnChange<T> = (args: { newState: T; oldState: T }) => void |
|
|
| export type Store<T> = { |
| getState: () => T |
| setState: (updater: (prev: T) => T) => void |
| subscribe: (listener: Listener) => () => void |
| } |
|
|
| export function createStore<T>( |
| initialState: T, |
| onChange?: OnChange<T>, |
| ): Store<T> { |
| let state = initialState |
| const listeners = new Set<Listener>() |
|
|
| return { |
| getState: () => state, |
|
|
| setState: (updater: (prev: T) => T) => { |
| const prev = state |
| const next = updater(prev) |
| if (Object.is(next, prev)) return |
| state = next |
| onChange?.({ newState: next, oldState: prev }) |
| for (const listener of listeners) listener() |
| }, |
|
|
| subscribe: (listener: Listener) => { |
| listeners.add(listener) |
| return () => listeners.delete(listener) |
| }, |
| } |
| } |
|
|
