trilium/apps/client/src/widgets/react/NoteStore.ts

type Listener = () => void;

class NoteSavedDataStore {
    private data = new Map<string, string>();
    private listeners = new Map<string, Set<Listener>>();

    get(noteId: string) {
        return this.data.get(noteId);
    }

    set(noteId: string, value: string) {
        this.data.set(noteId, value);
        this.listeners.get(noteId)?.forEach(l => l());
    }

    subscribe(noteId: string, listener: Listener) {
        let set = this.listeners.get(noteId);
        if (!set) {
            set = new Set();
            this.listeners.set(noteId, set);
        }
        set.add(listener);

        return () => {
            set!.delete(listener);
            if (set!.size === 0) {
                this.listeners.delete(noteId);
            }
        };
    }
}

export const noteSavedDataStore = new NoteSavedDataStore();