client.js

function executeWithFetch(request) {
  // EXERCISE FOR THE READER
}

function executeWithAxios(request) {
  // EXERCISE FOR THE READER
}

function ClientBuilder() {
  return (function () {
    let baseUrl, headers, executor;
    return {
      forBaseUrl(_baseUrl) {
        baseUrl = _baseUrl;
      },
      withHeaders(_headers) {
        headers = _headers;
      },
      usingFetch() {
        executor = executeWithFetch;
      },
      usingAxios() {
        executor = executeWithAxios;
      },
      build() {
        return {
          post(endpoint, data) {
            return executor({
              url: `${baseUrl}${endpoint}`,
              data,
              method: 'POST',
              headers,
            });
          },
          get(endpoint, params) {
            return executor({
              url: `${baseUrl}${endpoint}`,
              params,
              method: 'GET',
              headers,
            });
          },
        };
      },
    };
  })();
}