Axios interceptor for refresh token when you have multiple parallel requests

axios.refresh_token.js

// for multiple requests
let isRefreshing = false;
let failedQueue = [];

const processQueue = (error, token = null) => {
  failedQueue.forEach(prom => {
    if (error) {
      prom.reject(error);
    } else {
      prom.resolve(token);
    }
  })
  
  failedQueue = [];
}

axios.interceptors.response.use(function (response) {
  return response;
}, function (error) {

  const originalRequest = error.config;

  if (error.response.status === 401 && !originalRequest._retry) {
      
      if (isRefreshing) {
        return new Promise(function(resolve, reject) {
          failedQueue.push({resolve, reject})
        }).then(token => {
          originalRequest.headers['Authorization'] = 'Bearer ' + token;
          return axios(originalRequest);
        }).catch(err => {
          return err
        })
      }

    originalRequest._retry = true;
    isRefreshing = true;

    const refreshToken = window.localStorage.getItem('refreshToken');
    return new Promise(function (resolve, reject) {
       axios.post('http://localhost:8000/auth/refresh', { refreshToken })
        .then(({data}) => {
            window.localStorage.setItem('token', data.token);
            window.localStorage.setItem('refreshToken', data.refreshToken);
            axios.defaults.headers.common['Authorization'] = 'Bearer ' + data.token;
            originalRequest.headers['Authorization'] = 'Bearer ' + data.token;
            processQueue(null, data.token);
            resolve(axios(originalRequest));
        })
        .catch((err) => {
            processQueue(err, null);
            reject(err);
        })
        .then(() => { isRefreshing = false })
    })
  }

  return Promise.reject(error);
});