To use Axios interceptors to handle 401 API errors and refresh access/JSON web tokens(JWTs) tokens in TypeScript/Javascript, you can do the following:

1. Import the axios library and create an instance of the axios object:

import axios from 'axios';

const instance = axios.create();

1. Define a function to refresh the access token using a refresh token:

function refreshAccessToken(refreshToken: string): Promise<string> {
  // Send a request to the server to refresh the access token using the refresh token
  return axios
    .post('/refresh-token', { refreshToken })
    .then((response) => response.data.accessToken);
}

1. Add an interceptor to the instance object to handle 401 errors. In the interceptor, check for a 401 error, and if one is found, refresh the access token using the refresh token and retry the original request:

instance.interceptors.response.use(
  (response) => response,
  (error) => {
    const originalRequest = error.config;

    if (error.response.status === 401 && !originalRequest._retry) {
      originalRequest._retry = true;
      const refreshToken = // Get the refresh token from storage

      return refreshAccessToken(refreshToken).then((accessToken) => {
        // Replace the access token in the original request config
        originalRequest.headers['Authorization'] = `Bearer ${accessToken}`;
        return instance(originalRequest);
      });
    }

    return Promise.reject(error);
  }
);

With this in place, whenever an Axios request returns a 401 error, the interceptor will automatically refresh the access token and retry the original request.

It's important to note, however, that this example is just a rough outline of how to use Axios interceptors to handle 401 errors and refresh access tokens in TypeScript. You will need to handle additional edge cases in a real-world application and implement proper error handling.

For more information, be sure to refer to Axios' official documentation on interceptors.