Node Web Development 2nd Edition: Chapter1 About Node

1. About Node
Rick Chang

2. 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

3. 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)

4. 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

5. Server-side JavaScript
RingoJS (http://ringojs.org/)
Based on Mozilla Rhino and written in
Java
Node
Based on Google V8

6. JavasScript
loosely typed
dynamically extendable objects
anonymous closures

7. Pub/Sub Pattern
pub.sub.js Result
foo 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

8. Extend Object
Dynamically
people.js
The employee works
hard
Drive vehicle
Result

9. 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!!

10. Node.js
CommonJS module system
Make variables local to a module
Demo code

11. Demo
parent.js example.js

12. 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
});

13. Benchmark
var http = require('http');
http.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('Hello Worldn');
}).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

14. Company
Yahoo!
LinkedIn
Replace Ruby on Rails to Node
Paypal

15. 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

16. 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

17. 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