Node.js: architecture, APIs, event loop, concurrency

excellent article!

An overview of Node.js: architecture, APIs, event loop, concurrency

by Dr. Axel Rauschmayer

• What its architecture looks like.
• How its APIs are structured.
  • A few highlights of its global variables and built-in modules.
• How it runs JavaScript in a single thread via an event loop.
• Options for concurrent JavaScript on this platform.

Promises are explained in more detail in “JavaScript for impatient programmers”.

Node.js documentation