Скачать или смотреть Middleware in Nodejs

Middleware is a crucial layer used in modern web applications to manage request–response workflows, enhance functionality, and secure data exchange between the client and server. In Node.js, middleware functions operate between the incoming request and the final response. They are commonly used for tasks such as logging, parsing JSON data, handling errors, validating inputs, checking user roles, and implementing authentication & authorization. Popular frameworks like Express.js allow developers to create and integrate custom middleware to control how each request flows through the application.

In React.js, middleware is primarily used in state management libraries like Redux, where it intercepts actions before they reach the reducer. This enables features such as asynchronous API calls, data caching, token handling, and managing authenticated user flows. React-based middleware improves performance and ensures smooth communication between the frontend and backend.

Authentication middleware ensures that only valid and authorized users can access protected routes. In Node.js, authentication is often implemented using JWT (JSON Web Tokens), session-based auth, OAuth, or third-party providers like Firebase and Auth0. Middleware verifies tokens, extracts user details, and restricts access depending on permissions. On the React side, authentication logic includes storing tokens securely, guarding routes, auto-redirecting unauthorized users, and maintaining global user state.

Together, these middleware layers create a secure, scalable, and efficient communication pipeline in full-stack applications—making Node.js + React.js a powerful combination for building modern, user-friendly, and secure web systems.