WHAT IS NODE.JS

Node.js is a platform built on Chrome’s JavaScript runtime for
easily building fast, scalable network applications.

Node.js uses an
event-driven, non-blocking I/O model that makes it lightweight and
efficient, perfect for data-intensive real-time applications that run
across distributed devices.
thread.

WHAT IS NODE.JS

• Created in 2009 by Ryan Dahl
• JavaScript that’s outside of the browser. It can be used to build web servers, command line interfaces, anything that exists outside the browser.
• Uses the Google V8 JavaScript engine to execute JS (super fast)
• Single-threaded, event-driven & non-blocking I/O model
• It is 40 % Js and 60 % C++

WHAT IS NODE.JS

• Open source (github)
• Cross-platform (Linux, FreeBSD, OSX, Windows, etc)
• JavaScript interpreter (make it accessible to web dev)
• console based (allows easy use of stdin, stdout pipe)
• supports modules (which allow building of frameworks)
• non-blocking
• primarily used to build network programs and tools

WHY NODE.JS

• You need a fast web server that can handle 100,000+ concurrent connections with ease
• You know JS already and need a web server
• Ideal applications
  • JSON APIs, streaming data, dashboard for stock trader
• ​Bad applications
  • CPU intensive operations (Calculating Pi to 100m digits, cognitive computing algorithms, etc.)

WHAT TO USE NODE FOR

• Ideal for building fast, scalable real-time applications
• Push technology over WebSockets 
• Handles two-way connections extremely well

SAMPLE APPLICATIONS

• Chat server
• API on top of object store like MongoDB
• Queueing inputs to a db when receiving large amounts of concurrent data — such as real-time analytics
• Server-side proxy (like NGINX)
• Use Node stack for single page app dev
• Excellent for prototyping!

TO BE OR NOT TO BE

SYNCHRONOUS

$db = $this->getDatabase();

$query = 'SELECT giant_field, COUNT(field) AS counter
    FROM massive_table mt
    LEFT JOIN even_bigger_table ebt ON mt.field1 = ebt.field2
    WHERE ebt.field3 = \'Zosia\'
    ORDER BY mt.date DESC
    HAVING counter > 1000';

$result = $db->query($query)->fetchAll();

TO BE OR NOT TO BE

WHAT SERVER'S CPU IS DOING

Node.js Eveny loop

EVENT LOOP CPU UTILIZATION

• JuSt small gaps for context switching

• One thread, many consequent requests

• Separated IO operations

ONE REQUEST MEMORY USAGE

Node.js vs Apache2

Node.js vs Apache2

Node.js is *FAST*

• V8 based JS runtime
• Event driven
• Non-blocking I/O

NODE.JS REPL

A Read-Eval-Print-Loop (REPL) stand alone program comes with node and can be run via command line.

➜ node
> 2 + 4
6
> console.log("Hello")
"Hello"
> function sayHi(message){console.log(message)}
undefined
> sayHi("Hi There")
"Hi There"

CREATING & EXECUTING A NODE.JS FILE

A Node.js file is just a Javascript file. It's identical in most ways to client-side Javascript files. Example:

var testing = 12345;
function printStuff(stuff){
    console.log(stuff);
}
printStuff(testing);

Execute a JS file with Node.js:

➜  ~ node app.js

NODE MODULES

• Modules allow you to bring in external functionality into your Node app
• Modules can export variables, functions and objects 
• Three main sources of Node modules
  • Node’s built-in modules — fs, http, os
  • Third party modules from npm
  • Creating your own modules
• Modules are a great way to organize your code

USING MODULES

• Create a function, make it available with either exports or module.exports
• Use it with require

// create module hello.js
var hello = function(){
   console.log('hello!') 
}; 
module.exports = hello;

// use the module in your main server file
var hello = require('./hello');
hello();
  

CREATING A MODULE

To expose your module of javascript code for other files to import/use, you need to use the 'module.exports' command:

//superhero.js

var superhero = {
    saveTheDay: function (arg1, arg2, arg3){
        //do something supernatural
        //display that supernatural thing
    }
}

module.exports = superhero;

COMMONJS FORMAT

• Node.js uses the CommonJS format for modularity
• Importing a module into your file:

require('./relative/path/to/module');

This module can now be used in your file:

var instanceOfSuperhero = require('./js/superhero');

instanceOfSuperhero.saveTheDay('Location', 'Time', 'Person');

IMPORTING MODULES BASED ON ORIGIN

Core Node Modules (Like 'http'):

require('http');

Your custom modules

require('./relative/path/to/module');

3rd party modules installed via NPM (stored in 'node_modules'' folder):

require('express');

NPM

• Node Package Manager (NPM) is the official repository for server-side JS, with tons of client-side JS as well
• Common NPM modules include ExpressJS, Mongoose, Cordova, Grunt, Gulp and Browserify.
• The NPM ecosystem is completely open and anyone can create a package for others to use
• It makes your life as a developer 1 billion times easier :)

PACKAGE.JSON

• To use NPM for your Node.js application, you must use a 'package.json' file to track the modules you use.
• This file can also be used to store mountains of other useful info about your application like the author's name, git repository, license and much more.
• After this file is created, a folder named 'node_modules' will be created to store modules you download/install

EXAMPLE PACKAGE.JSON

{
  "name": "browserify",
  "version": "10.2.4",
  "description": "browser-side require() the node way",
  "main": "index.js",
  "repository": {
    "type": "git",
    "url": "http://github.com/substack/node-browserify.git"
  },
  "keywords": [
    "browser"
  ],
  "dependencies": {
    "browser-pack": "^5.0.0",
    "vm-browserify": "~0.0.1",
    "xtend": "^4.0.0"
  },
  "author": {
    "name": "James Halliday",
  },
  "scripts": {
    "test": "tap test/*.js"
  }
}

CREATING PACKAGE.JSON

To create, use 'npm init' command:

➜  ~ npm init

Follow the prompts from there to create your file.

USING NPM

To download a package to your local machine:

npm install packagename

Install multiple packages:

npm install package1 package2 package3 etc

To record packages to 'package.json' file:

npm install packagename --save

USING A FRAMEWORK WITH NODE.JS

• NPM is full of enterprise grade 3rd party frameworks for everything you can think of - handling HTTP connections, interacting with databases, social media APIs, authentication, you name it.
• We will use a popular web framework for building Node.js applications called Express.

EXPRESS.JS

• Built-in HTTP server
• Request / response enhancements
• View support
• HTML & redirection helpers
• Ability to create robust APIs quickly & easily
• Model - View - Router architecture
• Does not hide any Node functions

EXPRESS

• Express is the most popular web framework for Node.js
• It has a simple API to for HTTP communications in Node.js

var express = require('express');
var app = express();

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

app.listen(3000);

EXPRESS

var express = require('express');
var app = express();

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

var server = app.listen(3000, 'localhost', function () {
    var host = server.address().address;
    var port = server.address().port;
    console.log(`Example app listening at http://${host}:${port}`);
});

Another example

INSTALL EXPRESS WITH NPM

Installing Express with NPM

npm install express --save

The '--save' flag will save this as a dependency in your 'package.json' file. Open it up to check it out

CREATING A SERVER WITH EXPRESS

• Use the Express API Docs to expand its capabilities and build your own creation.
• It's helpful to use nodemon to automatically restart your server when changes are made.

Get Method

var express = require('express');
var app = express();
var bodyParser = require('body-parser');

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

app.use(bodyParser.json()); // for parsing application/json

// for parsing application/x-www-form-urlencoded
app.use(bodyParser.urlencoded({ extended: true }));

app.get('/get_method', function (req, res) {
    res.send(`Hello ${req.query.name}`);
});

var server = app.listen(3000, 'localhost', function () {
    var host = server.address().address;
    var port = server.address().port;
    console.log(`Example app listening at http://${host}:${port}`);
});