Node.js® is a JavaScript runtime built on Chrome's V8 JavaScript engine. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient. Node.js’ package ecosystem, npm, is the largest ecosystem of open source libraries in the world.

Connect 是一个基于 HTTP 服务器的工具集,成为中间件(middleware)。

中间件,其实就是一个简单的 JavaScript 函数。除了处理 req 和 res 对象之外,还接受一个 next 函数来做流控制。