"mini store" - a ridiculously simple global store implementation

ministore.ts

export type ActionFunction<T> = (prev: T) => T;

export type Store<T> = {
  getState: () => T;
  setState: (action: T | ActionFunction<T>) => void;
  subscribe: (callback: VoidFunction) => VoidFunction;
};

export const createStore = <T extends unknown>(initialState: T): Store<T> => {
  let state = initialState;

  const callbacks = new Set<() => void>();
  const getState = () => state;

  const setState = (nextState: T | ActionFunction<T>) => {
    state =
      typeof nextState === "function"
        ? (nextState as ActionFunction<T>)(state)
        : nextState;

    callbacks.forEach((callback) => callback());
  };

  const subscribe = (callback: () => void) => {
    callbacks.add(callback);
    return () => {
      callbacks.delete(callback);
    };
  };

  return { getState, setState, subscribe };
};

TestComponents.tsx

import { ActionFunction, createStore } from "./ministore";
import { useStore } from "./useStore";

let store = createStore({ count: 0 });

export function ComponentA() {
    const [state, setState] = useStore(store);

    const inc = () => {
        setState((prev) => ({
            ...prev,
            count: prev.count + 1,
        }));
    };

    return (
        <div>
            <h1>Component - A</h1>
            <h1>{state.count}</h1>
            <button onClick={inc}>+1</button>
        </div>
    );
}

export const ComponentB = () => {
    const [state, setState] = useStore(store);

    const inc2 = () => {
        setState((prev) => ({
            ...prev,
            count: prev.count + 2,
        }));
    };

    return (
        <div>
            <h1>Component - B</h1>
            <h1>{state.count}</h1>
            <button onClick={inc2}>+2</button>
        </div>
    );
};

useStore.tsx

import { useEffect, useState } from "react"
import { Store } from "./ministore";

export const useStore = <T extends unknown>(store: Store<T>) => {
    const [state, setState] = useState(store.getState());

    useEffect(() => {

        const unsubscribe = store.subscribe(() => {
            setState(store.getState());
        });

        setState(store.getState());

        return unsubscribe;
    }, [store]);

    return [state, store.setState] as const;
}