Please correct me if I'm wrong. But you'd better avoid creating extra promises for performance reasons

  const promiseMap<key, Promise<any>> = new Map();

  async function keyedDebounce<R>(key: string, fn: () => R) {
    const existingPromise = promiseMap.get(key);
    if (existingPromise) return existingPromise;
  
    const promise = fn().then(result => {
      promiseMap.delete(key);
  
      return result;
    });
  
    promiseMap.set(key, promise);
  
    return promise;
  }