Signals

const store = createStore({ items: [] }, {
  // Signal with handler: (state, ...args) => Partial<T>
  addItem: (state, item: string) => ({
    items: [...state.items, item]
  }),
});

// Dispatch: returns Promise
await store.addItem('hello');

// Stack handlers on the same signal (command pipeline)
store.addItem.add((state, item) => {
  console.log(`Added: ${item}`);
  return state; // return state to pass through
});

Signals are named async commands on the store.

• Each signal is both callable (store.signal(args)) and a Signal instance (store.signal.add(handler))
• Handlers receive (state, ...args) and return Partial<T> or Promise<Partial<T>>
• Multiple handlers on one signal execute sequentially, results are merged
• Handlers can return void for side effects
• Async handlers (Promises, async/await, generators) are awaited automatically
• Signals return the updated store state, not raw data — always read from getState():

// Signal updates the store — read state from the store
await store.addItem('hello');
const { items } = store.getState();

String array vs record definition

// Record: handlers attached at creation
createStore(state, { add: (s, item) => ({ items: [...s.items, item] }) });

// Array: just names, add handlers later
createStore(state, ['add', 'remove']);
store.add.add((state, item) => ({ items: [...state.items, item] }));

See also: Store, Middleware.