redux-observable.js

const oauthUserEpic = (action$) =>
  action$
    .ofType(OAUTH_USER)
    .concatMap(({ token }) =>
      get({
        endpoint: 'user',
        params: { access_token: token }
      }) // assuming get() returns an Observable
      .map((user) =>
        addUser(
          user.set('access_token', token)
        )
      )
    });