A fast, unopinionated, minimalist web framework for Node.js.
Express.js is a back-end web application framework for Node.js. It simplifies the process of building robust APIs and web applications by providing essential features like routing, middleware, and view engine integration. It is known for its **minimalism** and flexibility, allowing developers to choose their own tools for databases, templating, and authentication.
Express provides a simple, yet powerful, mechanism for defining routes based on HTTP methods (GET, POST, PUT, DELETE) and URL paths. This allows the server to efficiently direct incoming client requests to the correct functions and resources.
Middleware is a core concept. These functions have access to the request (`req`), response (`res`), and the next middleware function (`next`). They are used for tasks like logging, authentication, data validation, and handling CORS headers before the request hits the final route handler.
Express is deliberately lightweight and **unopinionated**. It doesn't force a specific structure or technology (like a particular database or templating engine). This allows developers maximum flexibility to choose the libraries and architecture that best suit their project needs.
Express provides convenience methods for handling HTTP tasks, such as `res.send()`, `res.json()`, and `req.params`. These methods streamline the process of sending data back to the client and extracting necessary data from the incoming requests.