Express

Express is a fast, unopinionated, minimalist web framework for Node.js. This flexible web application framework belongs to the Node.js Incubating Project. Express has 3 main features.

The first one is the basic middleware pattern. Through the route handlers and its aspect of declarative routing, the user can provide multiple callback functions that might invoke next('route') to bypass the remaining route callbacks, and behave like middleware while handling a request.

The user can use this mechanism to impose pre-conditions on a route, then pass control to subsequent routes if there’s no reason to proceed with the current route. The second feature is the myriad of HTTP methods that mixed with the middleware behaviour make creating a robust API quick and easy.

The third and final important feature is the thin layer of fundamental application features that Express provides. These features can be compared to a sugar layer on top of the Node.js http server, that boost performance without obscuring Node.js features.