Agenda

  • Why,  When and What's Node.js?
  • Node.js Hello World
  • What's and how to use NPM
  • Dependencies with Common.js
  • Callbacks, callbacks and more callbacks
  • Express.js to the rescue
  • Going real time with Socket.io

Why Node.js

Why, When and What's Node.js

Why Node.js

Why, When and What's Node.js

Why Node.js

Why, When and What's Node.js

Why Node.js

Why, When and What's Node.js

Companies using Node.js

Why Node.js

Why, When and What's Node.js

Why, When and What's Node.js

Why Node.js

Callback

Blocking I/O

Why Node.js

Why, When and What's Node.js

Why Node.js

Why, When and What's Node.js

How to scale ?

When Node.js

Why, When and What's Node.js

When Node.js

Why, When and What's Node.js

What's Node.js

Why, When and What's Node.js

NODE.JS SYSTEM ARCHITECTURE

What's Node.js

Why, When and What's Node.js

What's Node.js

Why, When and What's Node.js

What's Node.js: A Hello Node App

Why, When and What's Node.js

// See node-lessons/lesson_0/index.js
var http = require('http');

var PORT = process.env.PORT || 8080;
var HOSTNAME = process.env.HOSTNAME || 'localhost';
var NODE_ENV = process.env.NODE_ENV || 'development';
var counter=0;

var server = http.createServer(function(request, response) {
  response.writeHead(200, {'Content-Type': 'text/html'});
  response.write('<!DOCTYPE "html">');
  response.write('<html>');
  response.write('<head>');
  response.write('<title>Hello Node Page</title>');
  response.write('</head>');
  response.write('<body>');
  response.write('Hello Node.js ' + counter + ' running as ' + NODE_ENV + '!');
  response.write('</body>');
  response.write('</html>');
  response.end();
  console.log('counter: ' + counter + ' request url: ' + request.url);
  counter++;
});

server.listen(PORT, HOSTNAME);
console.log('Server is listening at PORT:' + PORT);

What are Node.js modules

Why, When and What's Node.js

  • 1 to 1 correspondence with 1 file
  • Modules are loaded synchronously
  • Modules are cached
  • Core modules come with the platform
  • 3rd party modules are published as packages to a registry (such as NPM)
    • use:npm install
    • installed into node_modules directory
  • ​File modules
    • require path starts with '/', './', or '../'

How require(...) works?

Why, When and What's Node.js

If not a core module, and not an explicit path (whether absolute or relative):

  • Looks in module's directory for node_modules/
  •  if not found, continue searching  each parent directory until file system root ( / )
  • Throw an error (code: MODULE_NOT_FOUND)

How require(...) works?

Why, When and What's Node.js

When requiring a path instead of an explicit file

  • Look for package.json ("main" property)
  • Look for index.js
​EX:  require('./my_awesome_lib')

Folder as module

// example content of ./my_awesome_lib/package.json

{ "name" : "my-awesome-library",
  "main" : "./implementation/my_lib_impl.js" }

How require(...) works?

Why, When and What's Node.js

Modules can be installed globally using:

  • npm install -g [module_name]                                    

But that's just recommended for Command Line Interface (CLI) modules

EX:  npm install -g express-generator

If NODE_PATH is set with a single or multiple paths, Node.js will search there. Additionally it will also search in the following paths:

  1. $HOME/node_modules                                                                  
  2. $home/node_library
  3. #prefix/lib/node

 

Global modules

No longer considered a good practice but still there for legacy support.

How require(...) works?

Why, When and What's Node.js

What's NPM

"Do one thing well." 

 

"Compose larger units out of smaller, independent units of functionality."

NPM filosofy

Using NPM

# It shows up current NPM installed version
npm --version

# Initialize current folder creating 
# a package.json file to store dependencies
npm init

# Shows up NPM configuration like used 
# folders
npm config list

# List every globally installed module
npm list --g[lobal]

# List every locally installed module
npm list

# Locally installs express and also adds it 
# to package.json
npm install express --save

# Locally installs specific modules but 
#just for dev environments
npm install mocha chai --save-dev

# Installs all dependencies declared at 
# package.json even dev dependencies 
npm install

# Just installs non development 
# specific dependencies.
npm install --production

# Locally uninstall a module
npm uninstall express

# Installs a particular module version
npm install underscore@1.8.2

# Updates a module but following what's 
# configured at package.json
npm update underscore

More about NPM

THE SIMPLEST MODULE

Dependencies with Common.js

// See node-lessons/lesson_1/hello.js
console.log('Hello World');
// See node-lessons/lesson_1/app.js
require('./hello.js');
>node app.js
Hello World
>

PATTERN 1: DEFINE A GLOBAL

Dependencies with Common.js

// See node-lessons/lesson_2/foo.js
foo = function () {
    console.log('foo!');
}
// See node-lessons/lesson_2/foo.js
require('./foo.js');
foo();
>node app.js
foo!
>

PATTERN 2: EXPORT AN ANONYMOUS FUNCTION

Dependencies with Common.js

// See node-lessons/lesson_3/bar.js
module.exports = function () {
    console.log('bar!');
}
// See node-lessons/lesson_3/app.js
var bar = require('./bar.js');
bar();
>node app.js
bar!
>

PATTERN 3: EXPORT A NAMED FUNCTION

Dependencies with Common.js

// See node-lessons/lesson_4/fiz.js
exports.fiz = function () {
    console.log('fiz!');
}
// See node-lessons/lesson_4/app.js
var fiz = require('./fiz.js').fiz;
fiz();
>node app.js
fiz!
>

PATTERN 4: EXPORT AN ANONYMOUS OBJECT

Dependencies with Common.js

// See node-lessons/lesson_5/buz.js
var Buz = function () {};

Buz.prototype.log = function () {
    console.log('buz!');
};

module.exports = new Buz();
// See node-lessons/lesson_5/app.js
var buz = require('./buz.js');
buz.log();
>node app.js
buz!
>

PATTERN 5: EXPORT A NAMED OBJECT

Dependencies with Common.js

// node-lessons/lesson_6/baz.js
var Baz = function () {};

Baz.prototype.log = function () {
    console.log('baz!');
};

exports.Baz = new Baz();
// node-lessons/lesson_6/app.js
var baz = require('./baz.js').Baz;
baz.log();
>node app.js
baz!
>

PATTERN 6: EXPORT AN ANONYMOUS PROTOTYPE

Dependencies with Common.js

// See node-lessons/lesson_7/doo.js
var Doo = function () {};

Doo.prototype.log = function () {
    console.log('doo!');
}

module.exports = Doo;
// See node-lessons/lesson_7/app.js
var Doo = require('./doo.js');
var doo = new Doo();
doo.log();
>node app.js
doo!
>

PATTERN 7: EXPORT A NAMED PROTOTYPE

Dependencies with Common.js

// See node-lessons/lesson_8/qux.js
var Qux = function () {};

Qux.prototype.log = function () {
console.log('qux!');
};

exports.Qux = Qux;
// See node-course/node-lessons/lesson_8/app.js
var Qux = require('./qux.js').Qux;
var qux = new Qux();
qux.log();
>node app.js
qux!
>

exports VS module.exports

Dependencies with Common.js

module.exports.fiz = "fiz";
exports.buz = "buz";
module.exports === exports;
  • exports is a reference to module.exports,
  • node automatically creates it as a convenient shortcut.
  • For assigning named properties, use either one.

WARNING

Dependencies with Common.js

$ node
> module.exports.qux = "qux";
> exports
{ qux: "qux" }
> exports === module.exports
true
> exports = "wobble wibble wubble!";
> exports === module.exports
false
> exports
"wobble wibble wubble!"
> module.exports
{ qux: "qux" }
// module.exports is canonical
  • Assigning anything to exports directly (instead of exports.something) will overwrite exports reference so exports properties will not be seen from module.exports or available using require.

Callback Hell / Bumeran Code / 

Callbacks, callbacks and more callbacks

Callbacks Hell / Bumeran Code

Callbacks, callbacks and more callbacks

// Improving code readability

function x (a) {
    do_something(function(){
        process(a);
    });
}


// can be converted to this:

function x (a) {
    do_something(y_maker(a)); // notice we're calling y_maker,
                              // not passing it in as callback
}

function y_maker (b) {
    return function () {
        process(b);
    };
}

Callbacks

Callbacks, callbacks and more callbacks

Async.js to the rescue

Callbacks, callbacks and more callbacks

Async provides around 70 functions that include the usual 'functional' suspects:

  • map
  • reduce
  • filter
  • each
  • parallel
  • series
  • waterfall

As well as some common patterns for asynchronous control flow:

Async.js : series

Callbacks, callbacks and more callbacks

// See node-lessons/lesson_9/async_series.js
var async = require('async');

async.series([
    function(callback){
        console.log('1st function call starts.');
        setTimeout(function(){
            console.log('1st function call resolved.');
            callback(null, 1); // err, result
        }, 1000);
    },
    function(callback){
        console.log('2nd function call starts.');
        setTimeout(function(){
            console.log('2nd function call resolved.');
            callback(null, 2, 3); // err, results
        }, 100);
    }
],
function(err, results){
    // err propagates all errors within the series functions
    // results holds all the results, [1, [2, 3]] in this case
    console.log('Results return in order as espected ;)');
    console.dir(results);
});

Async.js : parallel

Callbacks, callbacks and more callbacks

// See node-lessons/lesson_9/async_parallel.js
var async = require('async');

async.parallel([
    function(callback){
        console.log('1st function call starts.');
        setTimeout(function(){
            console.log('1st function call resolved.');
            callback(null, 1); // err, result
        }, 1000);
    },
    function(callback){
        console.log('2nd function call starts.');
        setTimeout(function(){
            console.log('2nd function call resolved.');
            callback(null, 2); // err, result
        }, 100);
    }
],
function(err, results){
    // err propagates all errors within the parallel functions
    // results holds all the results, [1, 2] in this case
    console.log('But results return in order as espected ;)');
    console.dir(results);
});

Async.js : waterfall

Callbacks, callbacks and more callbacks

// See node-lessons/lesson_9/async_waterfall.js
var async = require('async');
var WINK = ';)';
var SMILEY = ':D';
var TONGUE = ':P';

async.waterfall([
    function(callback){
        console.log('1st function call starts.');
        setTimeout(function(){
            console.log('1st function call resolved.');
            callback(null, WINK, SMILEY); // err, result, ... cascade params
        }, 5000);
    },
    function(arg1, arg2, callback){
        console.log(['2nd function call starts receiving arg1:',
            arg1,
            'and arg2:',
            arg2,
            '.'].join(' '));
        setTimeout(function(){
            console.log('2nd function call resolved.');
            var prefix = 'result ';
            callback(null, 
                prefix + TONGUE, 
                prefix + arg2, 
                prefix + arg1); // err, ... multiple results is ok
        }, 3000);
    }
],
function(err, result1, result2, result3){
    // err propagates all errors within the waterfall functions
    console.log('Important: waterfall can handle multiple results.');
    console.dir(result1);
    console.dir(result2);
    console.dir(result3);
});

More about Async.js?

Callbacks, callbacks and more callbacks

Express.js

Fast, unopinionated, minimalist web framework for Node.js

Express.js to the rescue

https://github.com/subfuzion/express-demo

Express.js to the rescue

# Installing Express in our project
npm install express --save

# Do you need a middleware for handling JSON, Raw, Text and URL encoded form data?
npm install body-parser --save

# Do you need a middleware to parse cookies from request headers and populate 
# req.cookies with an object keyed by the cookie names?
npm install cookie-parser --save

# Do you need a middleware for handling multipart/form-data?
npm install multer --save

# Do you need session handling using cookie store?
npm install cookie-session --save

# Do you need server logs?
npm install morgan --save

# Do you need to serve static content (i.e. html pages, images, css)?
npm install serve-static --save
 
# Do you need an authentication library?
npm install passport --save

# Do you want CLI assistance to create your App?
# then globally install express and express-generator
npm install -g express express-generator

Preflight check on

Express.js to the rescue

//server.js
var express = require('express');
var app = express();

app.get('/', function (req, res) {
   res.send('Hello World');
})

var server = app.listen(8081, function () {

  var host = server.address().address
  var port = server.address().port

  console.log("Example app listening at http://%s:%s", host, port)

})

First flight on Express.js

See lesson_10 source code

See lesson_11 source code

Express.js to the rescue

What is Middleware

Middleware pattern is a series of processing units connected together, where the output of one unit is the input for the next one. In Node.js, this often means a series of functions in the form:

function(request, response, next) {
 // ... Run some code
 next();
};

request -> middleware1 -> middleware2 -> ...middlewareN -> route -> app -> response

Tipical Flow:

Express.js to the rescue

Applying Express middleware

var express = require('express');
var app = express();
//... Define middleware1-N
app.use(middleware1);
app.use(middleware2);
...
app.use(middlewareN);

          Express leverages the

Connect framework

to provide the  middleware

functionality.

Express.js to the rescue

Middleware order

var express = require('express');

var logger = require('morgan');
var bodyParser = require('body-parser');

var app = express();
...

app.use(logger('dev'));
app.use(bodyParser.json());

Middlewares are executed in the specified order:

Express.js to the rescue

Two Categories of Express Middleware

  1. npm modules, e.g., body-parser
  2. Custom Middleware

See lesson_13 source code for an express-generator example

Express.js to the rescue

Custom Middleware

Creating a Custom Middleware using a reference

Creating a Custom Middleware with anonymous function definition

...
var middleware = function (request, response, next) {
 // Modify request or response
 // Execute the callback when done
 next();
};
...
app.use(middleware);
app.use(function (request, response, next) {
 // Modify request or response
 // Execute the callback when done
 next();
});

Express.js to the rescue

Template Engines

Some examples

Express.js to the rescue

Template Engines

Express.js uses by default

PUG ???... really? ... well ... yes

JADE

Express.js to the rescue

Template Engines: JADE

Express.js to the rescue

Template Engines: JADE/PUG

//-index.jade
doctype html
html(lang="en")
  head
    title= pageTitle
  script(src="/scripts/force.js")
  script.
    var useTheForce = force.use();
  body
    h2 These aren't the droids you're looking for
    #container.col
      p -You can go about your busines.
      p -Move along. 

May the force be with you and move to node-lessons/lesson_12

Collection

Document

MongoDB query

Typical SQL query

MongoDB query with projection control

MongoDB insert

MongoDB update

MongoDB remove

MongoDB aggregated query

MongoDB map reduce query

MongoDB documents relationship

var mongoose = require('mongoose');
var Schema = mongoose.Schema;

// create a schema
var userSchema = new Schema({
  name: String,
  username: { type: String, required: true, unique: true },
  password: { type: String, required: true },
  admin: Boolean,
  location: String,
  meta: {
    age: Number,
    website: String
  },
  created_at: Date,
  updated_at: Date
});

// the schema is useless so far
// we need to create a model using it
var User = mongoose.model('User', userSchema);
// make this available to our users in our Node applications
module.exports = User;

Mongoose

// if our user.js file is at app/models/user.js
var User = require('./app/models/user');
  
// create a new user called chris
var chris = new User({
  name: 'Chris',
  username: 'sevilayha',
  password: 'password' 
});

// call the custom method. this will just add -dude to his name
// user will now be Chris-dude
chris.dudify(function(err, name) {
  if (err) throw err;
  console.log('Your new name is ' + name);
});

// call the built-in save method to save to the database
chris.save(function(err) {
  if (err) throw err;
  console.log('User saved successfully!');
});

Mongoose

Socket.io main objective

Socket.io main objective is to enable real time applications on any browser

  • Socket between Server & Client
  • Send data between clients
  • Receive event based data
  • Supports almost any browser
  • Supports Multiple sockets on a single connection
  • Detects disconnection using heartbits
  • 100% javascript
  • Available on NPM

Socket.io typical usage

Socket.io is real time

Socket.io fallback methods

Socket.io handshake

client socket.io

Node.js server + socket.io

Socket.io handshake

client socket.io

Node.js server + socket.io

transport getway, id and config are returned

Socket.io handshake

client socket.io

Node.js server + socket.io

Heartbeats sent to secure connection healt

client stablish a realtime connection with server

Basic server setup


var io = require('socket.io').listen(80);

io.sockets.on('connection', function (socket){

    socket.emit('helloworld', { hello: 'world' });

    socket.on('other event', function (data) {
        console.log(data);
    });
});

Basic client setup


<script src="/socket.io/socket.io.js"></script>

<script>
    var socket = io.connect('http://localhost');

    socket.on('news', function (data) {
        console.log(data);
        socket.emit('other event', { the: 'data' });
    });

</script>

?

Thanks

Node.js FUNdamentals (short version)

By Leonardo Daniel Otero

Node.js FUNdamentals (short version)

  • 824