run response interceptor only once when multiple API calls

Question

I have an interceptor like this

axios.interceptors.response.use(undefined, err=> {
    const error = err.response;
    console.log(error);
    if (error.status===401 && error.config && !error.config.__isRetryRequest) {
        return axios.post(Config.oauthUrl + '/token', 'grant_type=refresh_token&refresh_token='+refreshToken,
            { headers: {
          'Authorization': 'Basic ' + btoa(Config.clientId + ':' + Config.clientSecret),
          'Content-Type': 'application/x-www-form-urlencoded,charset=UTF-8'
         }
       })
        .then(response => {
          saveTokens(response.data)
          error.config.__isRetryRequest = true;
          return axios(error.config)
        })
      } 
  })

And everything is working, but if I have like in my case 4 API calls on one React Component, and this error happens the same code will be run 4 times, meaning 4 times I will send my refresh token and get the auth token, and I would want to run it only once obviously

Answer 1

I think you can queue authentication requests with something like:

let authTokenRequest;

// This function makes a call to get the auth token
// or it returns the same promise as an in-progress call to get the auth token
function getAuthToken() {
  if (!authTokenRequest) {
    authTokenRequest = makeActualAuthenticationRequest();
    authTokenRequest.then(resetAuthTokenRequest, resetAuthTokenRequest);
  }

  return authTokenRequest;
}

function resetAuthTokenRequest() {
  authTokenRequest = null;
}

And then in your interceptor...

axios.interceptors.response.use(undefined, err => {
  const error = err.response;
  if (error.status===401 && error.config && !error.config.__isRetryRequest) {
    return getAuthToken().then(response => {
      saveTokens(response.data);
      error.config.__isRetryRequest = true;
      return axios(error.config);
   });
  } 
});

I hope this helps you ;)