Node.js Workshop

© 2015 PayPal Inc. All rights reserved. Conﬁdential and proprietary.
Node.js Workshop
Quhan Arunasalam
March / 27 / 2015 NTU-IEEE

© 2015 PayPal Inc. All rights reserved. Conﬁdential and proprietary
Node.js
An open source, cross-platform
runtime environment for
server-side Javascript applications.
NPM A package manager for Javascript.
Express
A minimal and flexible Node.js
web application framework.
What we’re going to explore today
2

Node.js
Run Javascript on the server
3

Understanding the Event Loop
The guts of Node
4

Do
JSON based REST APIs
Web / Mobile-Web Apps
Network Apps
Don’t CPU intensive work
When to use Node?
5

Test the waters via REPL
The Read-Eval-Print Loop
6
• Provides a way to interactively
run JavaScript and see the
results.
• Useful for debugging,
testing, or just trying things
out.
https://www.flickr.com/photos/snype451/5752753663/

Lab 2.1: Test the waters via REPL
Read-Eval-Print-Loop
7
$
node

>
var
a
=
[1,
2,
3];

>
console.log(a);

[
1,
2,
3
]

>
a.forEach(function
(z)
{
console.log(z);
});

1

2

3

Lab 2.2: Baby-steps
Building the classic Hello World
8
$
mkdir
hello
&&
cd
hello

$
touch
index.js

//
index.js

console.log('Hello
NTU');

$
node
index

Hello
NTU
https://www.flickr.com/photos/munakz/9228501911/

The module system
The building blocks of a Node app
9
http://pixabay.com/en/lego-building-blocks-shapes-puzzle-297773/
• Makes it possible to include
other Javascript files into your
app.
• Helps organize your code into
separate parts with limited
responsibilities.
• Using modules is simple -
You just require() them.

Lab 2.3: Requiring things
Modifying your previous Hello World example
10
$
touch
greet.js

//
greet.js

exports.hello
=
function
()
{

return
'Hello
NTU';

}

//
index.js

var
greet
=
require('./greet.js');

console.log(greet.hello());

$
node
index

Hello
NTU

Lab 2.4: Requiring things (again)
Let’s get bilingual
11
//
greet.js

exports.hello
=
function
()
{

return
'Hello
NTU';

}

exports.konbanwa
=
function
()
{

return
'Konbanwa
NTU';

}

//
index.js

var
greet
=

console.log(greet.hello());

console.log(greet.konbanwa());

$
node
index

Hello
NTU

Konbanwa
NTU

Lab 2.5: Requiring things (one last time)
Another way of handling exports
12
//
greet.js

module.exports
=
{

hello:
function
()
{

return
'Hello
NTU';

},

konbanwa:
function
()
{

return
'Konbanwa
NTU';

}

};

In-built modules
Don’t worry, we’re getting to the fun parts
13
http://commons.wikimedia.org/wiki/File:AMC_V8_engine_360_CID_customized_um.JPG
Node ships with a number of
core modules. For example:
• console - Sends output to
stdout or stderr.
• http - Provides a server and
client for HTTP traffic.
• fs - Provides functions to
interact with the file system.

Lab 2.6: Create a better (Hello) World
By building a web server
14
//
index.js

var
http
=
require('http');

var
greet
=

http.createServer(function
(req,
res)
{

res.writeHead(200,
{'Content-‐Type':
'text/plain'});

res.end(greet.hello());

}).listen(8000);

console.log('Server
running
at
http://127.0.0.1:8000');

Reuse and share code
NPM
15

What is npm?
It’s 3 things actually
16
https://www.flickr.com/photos/kamshots/3096111340/
• A module registry, containing
a collection of open-source
code.
• A standard, to define
dependencies on other
packages.
• A package manager, for
locally installed modules.

The npmjs.com registry
Note the 134,726 packages available (at the time of screenshot)
17

Lab 2.7: Initializing your Hello World project
With metadata
18
$
npm
init

...

name:
(hello)

version:
(1.0.0)

description:
An
app
to
say
Hello
NTU

entry
point:
(index.js)

test
command:

git
repository:

keywords:
helloworld

author:
Quhan
Arunasalam

license:
(ISC)

Lab 2.8: Saving the moment
Installing and using a 3rd party module
19
$
npm
install
-‐-‐save
moment

//
index.js

var
http
=
require('http');

var
greet
=

var
moment
=
require('moment');

http.createServer(function
(req,
res)
{

res.writeHead(200,
{'Content-‐Type':
'text/plain'});

res.end('Hi!
It
is
now
'
+
moment().format('h:mm:ss
a'));

}).listen(8000);

© 2015 PayPal Inc. All rights reserved. Conﬁdential and proprietary 20
Figuring out package.json
{

"name":
"hello",

"version":
"1.0.0",

"description":
"An
app
to
say
Hello
NTU",

"main":
"index.js",

"scripts":
{

"test":
"echo
"Error:
no
test
specified"
&&
exit
1"

},

"keywords":
[

"helloworld"

],

"author":
"Quhan
Arunasalam",

"license":
"ISC",

"dependencies":
{

"moment":
"^2.9.0"

}

}

Let’s not publish another hello world
8814 packages available (at the time of screenshot)
21

Let’s not publish another hello world
Hiding away your little secrets
22
{

"name":
"hello",

"version":
"1.0.0",

"private":
true,

"description":
"An
app
to
say
Hello
NTU",

...

}

Express
Web app building, made easier
23

What is Express?
24
• A framework to help build web
applications.
• Is to Node what Sinatra / RoR is
to Ruby.
• Makes development easier with:
• Request routing
• Handling HTTP verbs
• And a whole lot more...
• Is made up of a series of
middleware calls.
http://pixabay.com/en/tunnel-light-speed-fast-auto-101976/

Lab 2.9: Expressive greetings
Modify your Hello World code to use Express
25
$
npm
install
-‐-‐save
express

//
index.js

var
express
=
require('express');

var
greet
=

var
app
=
express();

app.get('/',
function
(req,
res)
{

res.send(greet.hello());

});

app.listen(8000);

Middleware
Middleware
Middleware
ApplicationRequest Response
A function with access to the request object, the response object, and
the next middleware in line in the request-response cycle of an
application.

Lab 2.10: Building an API server
To list and save tasks. And yay! Finally done with the Hello World!
27
$
mkdir
tasks
&&
cd
tasks

$
npm
init

...

$
npm
install
-‐-‐save
express

$
npm
install
-‐-‐save
express-‐session

$
npm
install
-‐-‐save
body-‐parser

$
touch
index.js

Setting up the Express skeleton
28
//
index.js

var
express
=
require('express');

var
session
=
require('express-‐session');

var
bodyParser
=
require('body-‐parser');

var
app
=
express();

app.listen(3000,
function
()
{

console.log('API
server
started
on
port
3000');

});

Setting up middleware (and some dummy data)
29
...

var
app
=
express();

app.use(session({secret:
'ntu-‐ieee'}));

app.use(bodyParser.urlencoded({extended:
false}));

function
initializeTasks()
{

var
tasks
=
[];

tasks.push('Step
1:
Learn
Node');

tasks.push('Step
2:
Learn
NPM');

tasks.push('Step
3:
Learn
Express');

return
tasks;

}

app.listen(3000,
function
()
{

...

Listing out tasks via GET
30
...

app.get('/',
function
(req,
res)
{

if
(!req.session.tasks)
{

//
Tasks
not
found
in
session,
so
initialize
it

req.session.tasks
=
initializeTasks();

}

//
Returns
a
JSON
object
with
an
array
of
tasks

res.json({tasks:
req.session.tasks});

});

...

Testing it out by GETing a list of tasks (via Postman)
31

Add a task via POST
32
...

app.post('/task',
function
(req,
res)
{

if
(!req.session.tasks)
{

//
Tasks
not
found
in
session,
so
initialize
it

req.session.tasks
=
initializeTasks();

}

//
Assign
the
POSTed
task
to
the
newTask
variable

var
newTask
=
req.body.task;

//
Save
the
new
task
to
the
session
array
of
tasks

req.session.tasks.push(newTask);

//
Returns
a
JSON
object
with
an
array
of
tasks

res.json({tasks:
req.session.tasks});

});

...

Testing it out by POSTing a new task (via Postman)
33

Cheatsheet
https://github.com/nodeworkshop/node

© 2015 PayPal Inc. All rights reserved. Conﬁdential and proprietary.
For more information, please contact:
PayPal Singapore 
5 Temasek Boulevard #09-01, Suntec Tower Five, Singapore 038985
Quhan Arunasalam

Node.js Workshop

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