INTRO TO NODE.JS



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The GOAL of NODE.JS IS TO provide an easy way to build scaleable network programs





NODE.JS IS NOT ANOTHER WEB FRAMEWORK


NODE.JS IS:

A Web Server
TCP Server
Awesome Robot Server
Drone Controller
Command Line Application
Proxy Server
Steaming Server
VoiceMail Server
Music Machine
(any thing that has to deal with I/0)



WHY NODE.JS?

Non-Blocking I/O
Based On Chrome's V8 Engine
49,000+ Modules
Very Active Community
Supported on Mac, Linux, and Windows
One Language to Rule them All
JavaScript is the Language of the Web



Basic Example

Create helloworld.js with:
console.log('Hello World');
On the command line run
node helloworld.js
You should see
Hello World



Basic HTTP SERVER


var http = require('http');
 
var server = http.createServer(function (req, res) {
  res.writeHead(200);
  res.end('Hello World');
});
 
server.listen(4000);
* Running this script on my development box I can achieve 10,000+ requests per second with 100 concurrent connections without 
breaking a sweat.




What is 

Non-Blocking IO?

AND WHY SHOULD I CARE?



BLOCKING I/0

// Get Users - 20ms
$query = 'SELECT * FROM users WHERE id = ?';
$users = query($query, array($_GET['id']));
print_r($users);

// Get Activities - 130ms
$query = 'SELECT * FROM activities WHERE user_id = ? ORDER BY TIMESTAMP LIMIT 50';
$activities = query($query, array($_GET['id']));
print_r($activities);

// Get Leader Board - 120ms
$query = 'SELECT count(points),user_id FROM activities GROUP BY user_id LIMIT 50';
$leader_board = query($query);
print_r($leader_board);
270ms = SUM($user, $activities, $leader_board)


NON-BLOCKING I/0

// Get Users - 20ms
var query = 'SELECT * FROM users WHERE id = ?';
db.query(query, [req.query.id], function (err, users) {
    console.log(users);
});

// Get Activities - 130ms
query = 'SELECT * FROM activities WHERE user_id = ? ORDER BY TIMESTAMP LIMIT 50';
db.query(query, [req.query.id], function (err, activities) {
    console.log(activities);
});

// Get Leader Board - 120ms
query = 'SELECT count(points),user_id FROM activities GROUP BY user_id LIMIT 50';
db.query(query, function (err, leader_board) {
    console.log(leader_board);
});
130ms = MAX(user, activities, leader_board)






THE MOST JARRING THING ABOUT SERVER SIDE JAVASCRIPT IS THINKING IN CALLBACKS



The NODE.JS CALLBACK PATTERN

awesomeFunction(args, function (err, data) {
    if (err) {
        // Handle Error
    }
    
    // Do something awesome with the data
});
  • Error First then success... ALWAYS!
  • Because this is the defacto standard, 99.99999% of the time you will be able to guess how a Node.js module works




The Node Package manager

otherwise known as NPM!

NPM is how you harness the awesomeness of the Node.js community


USING NPM

It's standard practice to install modules locally for  your current project. Modules are installed in   ./node-modules in the current directory
To install a new module:  
npm install <module>
To find a module in the repo:  
npm find <module>
To list the modules (and depedancies) for the curent project:  
npm list


Basic Module Example

var currentCount = 0;

module.exports.incr = function () {
    return ++currentCount;
};
Once you've created a module in counter.js you use it like this... 
var counter = require('./counter');
counter.incr();
var count = counter.inrc();

Keep this in mind... modules are loaded once and cached. So when you load the module a second time in your app, require just returns the cached module object. This lets you do interesting things...



INSTALLING YOUR MODULES

Run npm link in the module directory. Then run 
npm link module in the project directory.

Add the module's Gitub URL to your package.json dependancies and run npm install.
"dependencies": {
    "my-module": "https://github.com/my-name/my-module/tarball/master"
}




CREATING YOU OWN MODULES


require('./example') will load either example.js or example/index.js or the entry point defined in package.json

Run npm init to bootstrap  your new module, this will create the package.json

Try to stick to creating "Pure JavaScript" module if possible. It will give you less headaches down the road





Questions?

Intro To Node.js

By Eric Schoffstall

Source: Chris Cowan

Intro To Node.js

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