refreshToken.js

const Api = function(params) {
  const _store_ = {
    accessToken: null,
  }
  
  return {
    getAccessToken() {
      return _store.accessToken
    },
    async login() {
      try {
        const response = await axios.post(
          'https://something.com/v1/auth',
          params,
        )
        return response.data
      } catch (error) {
        throw error
      }
    },
    async refreshToken() {
      try {
        const response = await axios.post(
          'https://something.com/v1/access_token/',
          params,
        )
        const { token } = response.data
        _store.accessToken = token
        return token
      } catch (error) {
        throw error
      }
    },
    setAccessToken(token) {
      if (token === undefined) {
        throw new Error('token is undefined')
      }
      _store.accessToken = token
    },
    // ...other methods
  }
}

const api = Api({
  username: 'bob',
  password: 'the_builder123',
})

api
  .refreshToken())
  .then((token) => console.log(token))
  .catch(console.error)