Authentication & Authorization with Axios in Node.js

const axios = require('axios');

// Create an axios instance
const api = axios.create({
    baseURL: 'https://api.example.com'
});

// Request interceptor
api.interceptors.request.use(
    config => {
        const token = localStorage.getItem('token');
        if (token) {
            config.headers.Authorization = `Bearer ${token}`;
        }
        return config;
    },
    error => {
        return Promise.reject(error);
    }
);

async function login(username, password) {
    try {
        const response = await axios.post('/auth/login', {
            username,
            password
        });

        const { token } = response.data;
        localStorage.setItem('token', token);

        return token;
    } catch (error) {
        console.error('Login failed:', error);
        throw error;
    }
}

api.interceptors.response.use(
    response => response,
    async error => {
        const originalRequest = error.config;

        if (error.response.status === 401 && !originalRequest._retry) {
            originalRequest._retry = true;

            const refreshToken = localStorage.getItem('refreshToken');
            const newToken = await refreshAccessToken(refreshToken);

            axios.defaults.headers.common['Authorization'] = `Bearer ${newToken}`;
            return api(originalRequest);
        }

        return Promise.reject(error);
    }
);

function checkPermission(requiredRole) {
    return async (req, res, next) => {
        const token = req.headers.authorization?.split(' ')[1];
        if (!token) {
            return res.status(401).json({ message: 'No token provided' });
        }

        try {
            const decoded = jwt.verify(token, process.env.JWT_SECRET);
            if (!decoded.roles.includes(requiredRole)) {
                return res.status(403).json({ message: 'Insufficient permissions' });
            }
            next();
        } catch (error) {
            return res.status(401).json({ message: 'Invalid token' });
        }
    };
}