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Node Web Development 2nd Edition: Chapter1 About Node
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About NodeRick Chang
What is Node
A Platform to write JavasScript applications outside web browsers.
No DOM
No bowser capability
Act as a web server
Care about HTTP headers
About Node
No thread (run single-threaded)
Event-driven architecture (publish/subscribe)
Google V8 JavaScript engine
Non-block I/O event loop (Asynchronous I/O)
File and network I/O libraries (use multiple threads)
History
Ryan Dahl created in 2009[1]
chose JavaScript because of the lack of an existing I/O API
Build high performance and scalable network applications
Sponsored by Joyent[2]
Inspired By seeing a file upload progress bar on Flickr
npm created by Isaac Schlueter, a package manager was introduced in 2011
Microsoft partnered to create a native Windows version in July 2011
Server-side JavaScript
RingoJS (http://ringojs.org/)
Based on Mozilla Rhino and written in Java
Node
Based on Google V8
JavasScript
loosely typed
dynamically extendable objects
anonymous closures
Pub/Sub Pattern
pub.sub.js Resultfoo 1 2 foo.bar 1 2 foo.baz 1 2 !foo.bar 3 4 !foo.baz 5 6 !foo 7 8 foo.baz 7 8
Extend Object Dynamically
people.js
The employee works hard Drive vehicle
Result
JavaScript vs Java
Java
Non-dynamic language
Static typed
The compiler catch programming mistakes
JavaScript
Dynamic language
Loosely typed
Global Object
Global Object cause an unruly chaos!!
Node.js
CommonJS module system
Make variables local to a module
Demo code
Demo
parent.js example.js
Asynchronous I/O
A single-thread event loop without thread context switch
Callback function to handle result
result = query('SELECT * from db'); // operate on the result
query('SELECT * from db', function (err, result) { if (err) throw err; // handle errors // operate on result });
Benchmark
var http = require('http'); http.createServer(function (req, res) { res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Hello World\n'); }).listen(8124, "127.0.0.1"); console.log('Server running at http://127.0.0.1:8124/');
Node Nginx
Throughput 822 req/sec 704 req/sec
Memory Used 64M 4M
Company
Yahoo!
Replace Ruby on Rails to Node
Paypal
Conclusion
Node is a great platform for I/O-bound applications
No good for computationally expensive calculations
Finbonacci sequence calcuation
More performance, fewer servers, lower cost and lower environment impact
Debate
Node.js favours performance over usability and robustness
Difficult to debug, refactor and develop
no synchronous code
duplicate callback
emitters may get multiple “error” events
missing “error” events sends everything to hell
“error” handlers are very verbose
Reference
[1]Node.js, http://en.wikipedia.org/wiki/Node.js
[2]Joyent, https://www.joyent.com/
[3]Farewell Node.js, TJ Holowaychuk, https://medium.com/code-adventures/farewell-node-js-4ba9e7f3e52b
[4]关于TJ⼤大神的Farewell Node.js, http://www.welefen.com/about-tj-farewell-node.js-article.html
[5]JavaScript模块化开发(⼆二)—CommonJS规范, http://www.feeldesignstudio.com/2013/09/javascript-module-pattern-commonjs
[6]CommonJS规范, http://javascript.ruanyifeng.com/nodejs/commonjs.html
