Introduction to Node js

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A K S H A Y M A T H U R
@AKSHAYMATHU
Getting Started with

Ground Rules
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 Post on FB and Tweet now
 Disturb Everyone during the
session
 Not by phone rings
 Not by...

Let’s Know Each Other
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 Do you code?
 OS?
 Node?
 JavaScript, JSON?
 Web Development?
 CoffeeScript
 ...

Akshay Mathur
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 Founding Team Member of
 ShopSocially (Enabling “social” for retailers)
 AirTight Neworks...

JavaScript
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 Born in 1995 at Netscape
 Not at all related to Java
 Syntax influenced by C
 Interpreted E...

Typical Usage
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 Web programing
 Client side
 Web pages
 Browser plugins
 Server side
 SSJS (not in use...

NodeJS
 JavaScript Runtime at command line
 Allows us to write JS programs outside browser
 Built on V8 JS engine
 V8 ...

Good for
 For IO heavy apps
 Web socket (chat) server
 Real time collaborative editor
 Fast file uploads
 Ad server
...

NodeJS is NOT
 A web framework
 Provides tools to create a web server
 Multi threaded
 Is Single threaded, event drive...

Possible Issues
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 Can not utilize multicore processer because of single
thread
 Managing multiple process...

S I N G L E T H R E A D E D
E V E N T D R I V E N
A S Y N C H R O N O U S
N O N - B L O C K I N G
What Jargons Mean

Single Threaded
 New Node process does not start for every request
 Only one code executes at a time
 Everything else r...

Non-blocking
 There is only one process that is executing
 If the process waits for something to complete, everything el...

Blocking Vs. Non-blocking
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var a = db.query('SELECT * from huge_table’);
console.log('result a:’, a);
conso...

Asynchronous
 Not all code is executed in the same order it is
written
 Node (and you) divide the code into small pieces...

Event Driven
 A code block gets into the queue of execution when
an event happens
 It gets executed on its turn
 Anyone...

The Event Queue
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‘King and Servants’ Analogy… by Felix Geisendörfer
everything runs in parallel, except your code. To understand that,
imag...

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D O T H E Y O C C U R O N S E R V E R A S W E L L ?
Events

Events we know…
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 The event familiar to us are
 Click
 Focus
 Blur
 Hover
 These events are raised wh...

Node Events
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 The most common event that a web server uses is
request
 Raised when a web request (url) hi...

Let’s Revise: JS Function Facts
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 Function is a block of a code that gets executed when
called
 JS functi...

Event Callback
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 Because the system is single threaded
 And we do not want to block it for I/O
 We use a...

Callback in Action
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callback = function(res) {
console.log('result a:’, res);
};
db.query('SELECT * from hu...

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N O T H I N G B U T L I B R A R I E S
Node Modules

Available Modules
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 Modules are nothing but collections of useful
functions
 Otherwise we call them libra...

Creating Custom Module
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 Write some useful code in a file
 Some function(s) achieving a goal
 Decide wha...

Using Modules
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 ‘require’ functions loads a module
 Whatever has been exported becomes available with
‘re...

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A S I M P L E W E B S E R V E R
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Let’s Program

Hello World
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 Just one line is needed to write to STDOUT
console.log(‘Hello World’)
 Running the file wit...

$Minimalistic HTTP Server @akshaymathu 34 var http = require("http"); on_request = function(request, response) { response.w...$

Improving the Server
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 Running this server with Node starts the server
node server.js
 The server always ...

Organizing Code
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 Rather than writing everything in single file, it is a
good idea to divide the code into...

Initial Server Module
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var http = require("http");
function start() {
function onRequest(request, response)...

Initial Startup File
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 As server became a module and exposes a start
function, we need to
 load server mo...

Let’s Revise: Parts of URL
https://sub.domain.com:8086/a/folder/file.html?key
=val&key=val2#some_place
 Protocol
 Sub-do...

Server – Router Interaction
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 For routing the requests based on URL, the router
must know pathname of the ...

Initial Router
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function route(pathname) {
console.log("About to route a
request for " + pathname);
}
expor...

Router Aware Server
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var http = require("http");
var url = require("url");
function start(route) {
function...

Making Router Available to Server
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 Router is made available as an argument (dependency) to
server’s ‘star...

Adding Request Handlers
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 The actual work of creating response for a request
will be done by Request Handl...

Initial Request Handlers
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function start() {
console.log("Request for 'start’.");
return "Hello Start";
}
f...

Including Handlers
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var server = require("./server");
var router = require("./router");
var requestHandlers...

Change in Server
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function start(route, handle) {
function onRequest(request, response) {
var pathname =
ur...

Real Routing
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function route(handle, pathname) {
console.log(”Routing request for " + pathname);
if (typeof...

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 Done 
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Did we do everything Correct?
 Nop 

What is wrong?
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function start(route, handle) {
function onRequest(request, response) {
var pathname =
url....

What are the problems?
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 The way ‘content’ is being collected and being
written to response, it forces to ...

The Right Way
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 The content should be written into response object
when the content becomes available
 So...

Corrected Server
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var http = require("http");
var url = require("url");
function start(route, handle) {
fun...

Corrected Router
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function route(handle, pathname, response) {
console.log(”Routing request for " + pathnam...

$Corrected Handlers @akshaymathu 56 function start(response) { db.query(”select * from huge_table”, function (error, stdout...$

 Done 
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Did we do everything Correct?
 Yep 

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Summary
 Node will require extra work and different thought
process
 But it will pay off for it
 Choose Node carefully ...

MVC in Node
 Express (Controller)
 Mongoose (Model)
 Jade (View)
 More …
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Thanks
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@akshaymathu