Rate limits

const MAXIMUM_TRY_COUNT = 3;
const URL = 'https://api.hub2.io/balance';
const CONFIGURATION = {
  method: 'GET',
  headers: {
    ApiKey: YOUR_API_KEY,
    MerchantId: YOUR_MERCHANT_ID,
    Environment: 'sandbox',
  },
};

async function requestWithRetry(numberOfTries = 0) {
  const response = await fetch(URL, CONFIGURATION);

  if (response.status === 429 && numberOfTries < MAXIMUM_TRY_COUNT) {
    // Retry-After is expressed in seconds; add 1 second of grace delay
    const retryAfterSeconds = parseInt(response.headers.get('retry-after') ?? '1', 10) + 1;
    await new Promise((resolve) => setTimeout(resolve, retryAfterSeconds * 1000));
    return requestWithRetry(numberOfTries + 1);
  }

  return response;
}

// Using the NestJS framework
import { HttpService } from '@nestjs/axios';
import { Injectable } from '@nestjs/common';
import { AxiosError, AxiosResponse } from 'axios';
import { lastValueFrom } from 'rxjs';

@Injectable()
export class Hub2Service {
  public static readonly MAXIMUM_TRY_COUNT: number = 3;

  constructor(private readonly http: HttpService) {}

  async getBalance(numberOfTries: number = 0): Promise<AxiosResponse> {
    const url: string = 'https://api.hub2.io/balance';
    const config = {
      headers: {
        ApiKey: YOUR_API_KEY,
        MerchantId: YOUR_MERCHANT_ID,
        Environment: 'sandbox',
      },
    };

    try {
      return await lastValueFrom(this.http.get(url, config));
    } catch (error) {
      const response: AxiosResponse | undefined = (error as AxiosError).response;
      if (response?.status === 429 && numberOfTries < Hub2Service.MAXIMUM_TRY_COUNT) {
        // Retry-After is expressed in seconds; add 1 second of grace delay
        const retryAfterSeconds: number = parseInt(response.headers['retry-after'] ?? '1', 10) + 1;
        await new Promise((resolve) => setTimeout(resolve, retryAfterSeconds * 1000));
        return this.getBalance(numberOfTries + 1);
      }
      throw error;
    }
  }
}