JavaScript: The Definitive Guide, 6th Edition

Asynchronous I/O with Node

Node is a fast C++-based JavaScript interpreter with bindings to the low-level Unix APIs for working with processes, files, network sockets, etc., and also to HTTP client and server APIs. Except for some specially named synchronous methods, Node’s bindings are all asynchronous, and by default Node programs never block, which means that they typically scale well and handle high loads effectively. Because the APIs are asynchronous, Node relies on event handlers, which are often implemented using nested functions and closures.^[23]

This section highlights some of Node’s most important APIs and events, but the documentation is by no means complete. See Node’s online documentation at http://nodejs.org/api/.

Obtaining Node

Node is free software that you can download from http://nodejs.org. At the time of this writing, Node is still under active development, and binary distributions are not available—you have to build your own copy from source. The examples in this section were written and tested using Node version 0.4. The API is not yet frozen, but the fundamentals illustrated here are unlikely to change very much in the future.

Node is built on top of Google’s V8 JavaScript engine. Node 0.4 uses V8 version 3.1, which implements all of ECMAScript 5 except for strict mode.

Once you have downloaded, compiled, and installed Node, you can run node programs with commands like this:

node program.js

We began the explanation of Rhino with its print() and load() functions. ...