trying to encapsulate a rest api in a backend class in a react-redux-thunk environment

backend.js

import axios from 'axios';

export default class backend {

    constructor(username, password) {

        this.client = axios.create({
            auth: {
                username,
                password
            }
        });

        this.username = username;
        this.password = password;
        this.loggedIn = false;
    }

    isLoggedIn() {

        this.client.get('http://api.tld/isLoggedIn?secret=schmuuuu')
        .then(
            result => {
                if (result.status === 200) {
                    this.loggedIn = true;

                    dispatch({
                        type: 'LOGIN_SUCCESS',
                        credentials: {
                            username: this.username,
                            password: this.password
                        }
                    })
                } else {
                    dispatch({type: 'LOGIN_ERROR'})
                }
            }
        )
    }
}

LoginActions.js

import backend from '../backend';


export const LOGIN_START = 'LOGIN_START';
export const LOGIN_ERROR = 'LOGIN_ERROR';
export const LOGIN_SUCCESS = 'LOGIN_SUCCESS';

export const CHANGE_USERNAME = 'CHANGE_USERNAME';
export const CHANGE_PASSWORD = 'CHANGE_PASSWORD';


const client = new backend()

export function doLogin(username, password) {

    console.log('doLogin');

    return dispatch => backend.doLogin();

}

export function changeUsername(username) {

    return {
        type: CHANGE_USERNAME,
        username
    }
}

export function changePassword(password) {

    return {
        type: CHANGE_PASSWORD,
        password
    }
}

store.js

import { createStore, combineReducers, applyMiddleware } from 'redux';
import thunk from 'redux-thunk';
import { LOGIN_START, LOGIN_SUCCESS, LOGIN_ERROR, CHANGE_USERNAME, CHANGE_PASSWORD } from './actions/LoginActions';

function LoginReducer(state = {
    username: '',
    password: '',
    isLoggedIn: false,
    loggingIn: false,
}, action) {

    switch(action.type) {
        case CHANGE_USERNAME:

            return {
                ...state,
                username: action.username
            };
        case CHANGE_PASSWORD:

            return {
                ...state,
                password: action.password
            };
        default:

            return { ...state };
    }
}