request-handler-share-promise.js

let refreshPromise = null;

const refreshAccessToken = () => {
  if (refreshPromise != null) {
    return refreshPromise;
  }
  
  refreshPromise = sendRefreshTokenRequest();
  refreshPromise.then((response) => {
    if (response.code !== 200) {
      refreshPromise = null;
      return false;
    }
    updateAccessToken(response);
    refreshPromise = null;

    return true;
  });
  
  return refreshPromise;
};