TypeScript API Fetcher (plus refresh token support even across multiple requests, the other requests will wait for the promise set by the first request to acquire the promise)

fetcher.ts

import { getJwtToken, removeJwtToken, setJwtToken } from '@/providers/auth-provider.ts';
import { backendUrl } from '@/utils/config.ts';
import type { JwtTokenModel } from '@/utils/models.ts';

export interface FetcherResponse<TData> {
  message: string;
  statusCode: number;
  data?: TData;
  error?: string;
  page?: number;
  limit?: number;
  totalItems?: number;
  totalPages?: number;
}

let refreshPromise: Promise<void> | null = null;

export const fetcher = async <TData>(url: string, options?: RequestInit): Promise<FetcherResponse<TData>> => {
  const jwtToken = getJwtToken();

  const response = await fetch(`${backendUrl}/${url}`, {
    ...options,
    headers: {
      'content-type': 'application/json',
      'accept': 'application/json',
      ...(jwtToken ? { 'authorization': `Bearer ${jwtToken.accessToken}` } : {}),
      ...(options?.headers ?? {}),
    },
  });

  if (response.status === 401 && jwtToken) {
    if (!refreshPromise) {
      refreshPromise = (async () => {
        const refreshResponse = await fetch(`${backendUrl}/auth/refresh`, {
          method: 'PUT',
          headers: {
            'content-type': 'application/json',
            'accept': 'application/json',
            'authorization': `Bearer ${jwtToken.refreshToken}`,
          },
        });

        if (refreshResponse.status === 200) {
          const responseJson = await refreshResponse.json() as FetcherResponse<JwtTokenModel>;

          setJwtToken(responseJson.data!);
        } else {
          removeJwtToken();

          throw { statusCode: 401, message: 'Unauthorized.' };
        }
      })();

      refreshPromise.finally(() => {
        refreshPromise = null;
      });
    }

    await refreshPromise;

    return fetcher(url, options);
  }

  if (response.status === 204) {
    return {
      message: 'No content.',
      statusCode: 204,
    };
  }

  const responseJson = await response.json() as FetcherResponse<TData>;

  if (!response.ok) {
    throw responseJson;
  }

  return responseJson;
};