A complete guide to Node.js

Complete Guide On Node.js
By:
Senior Developer
Prabin Silwal

What you should know before?
Javascript
Unix command

Installation:3way to install
• 1st way: Nodejs.org :
– You can download pre-compiled binary
– Easy installation
– Automatic configured environment
– But, updates require reinstallation
– And switching versions need reinstallation

2nd way : Version manager(nvm):
Install any version quickly
Switch version quickly
Easy install on Linux
But no widzard based installation(must use
command line interface)
And reinstall global modules when switching version
Install version manager then node

3rd way : Compile it from source(node)
Get absolute new node
Customize your installation
But you must be familiar with compiling process
And takes longer
And not easy to switch

Which is preferable?
• For mine 2nd way

Window installation:
• Download node.js
• Click install

Checking after installation?
• Run command
• Type “node” and hit enter
• Type “console.log(‘your text’)”

Note that previous installation process
needs re installation for new updates.

Installing using nvm in Linux(Not
wizard mode for Linux):

Make ready to install by following
command:
• sudo apt-get install git
• sudo apt-get install curl

Why node.js ?
• It is js with browser
• JS for both front end and backend (eg: using
jquery)
• Native support
• It’s fast because it’s mostly C code

What can you build?
•
•
•
•

Websocket server ( Like chat server)
Fast file upload client
Ad server
Any Real- Time Data Apps

What is Node.js not:
• Web framework
• For Beginners (it’s very low level)
• Multi- threaded (You can think of it as a single
threaded server)

Few variables you are familiar about
web browser:
• window : (Type in console of chrome)
The window object have functions and
attributes that have to do something with
window being drawn in screen.

• location: (Type in console of chrome)
The location object has all the information about url
that being loaded.

• document : (Type in console of chrome)
The document object contains all oh html displayed
in page

Now type in node console:
• It displays undefined message

Why not work in node?
• Because node is not just an instance , so
“global” is defined in node but not in chrome
console where you can get instance version of
global object called window.

• This global object has several functions (which
are not in chrome console)
• EG: require function: used to pull in different
javascript script files from your appliction

Some works on both:
• Eg: console

Note: local variable vs global
• Eg:
name = prabin; //global
Var name = prabin; //local

Node is Non-blocking: Blocking vs Noblocking 1

REQUIRING MODULES
var http = require('http'); //http.js
va r fs = require('fs'); // fs.js
How does ‘require’ return the libraries?
How does it find these files?

Custom Module Example:
• Prabin_App(base folder)
– Example.js
var say = require(‘./say_hello_module.js’); //say is assigned as object & has 2 properties :
softly and loudly which both are functions
say.softly(‘prabin’);
Say.loudly(‘PRABIN’);

– Say_hello_module(Module Folder)
• index.js
var hello = function (message)
{
console.log(‘say hello:’+message);
});
exports.slowly = hello;//we first declare hello as function and setting slowly to be value of
hello
exports.loudly = function(message)
{
console.log(‘SAY HELLO:’+message);
});

NPM: THE USERLAND SEA
“Core” is small. “Userland” is large.

Package manager for node
• Comes with node
• Module Repository
• Dependency Management
• Easily publish modules
• “Local Only”

INSTALLING A NPM MODULE
/Home/my_app
• $ npm install request
https://github.com/mikeal/request
Installs into local node_modules directory
---------------after installation------------------------------Home/my_app/node_modules/request
----For require/using in your app-----------------------------------/Home/my_app/app.js
va r request = require('request');//Loads from local
node_modules directory

LOCAL VS GLOBAL MODULE
• Install modules with executables globally:
$ npm install coffee-script –g //global
$ coffee app.coffee
Note: Global npm modules can’t be required

$ npm install coffee-script //Install locally

FINDING MODULES
• From npm command line:
$ npm search module_name
Eg: $ npm search request

DEFINING YOUR DEPENDENCIES
my_app/package.json
{
"name": "My App",
"version": "1",
"dependencies":
{
"connect": "1.8.7"
}
}
Then: $ npm install will installs it into the node_modules directory
i.e. my_app/node_modules/connect

• SEMANTIC VERSIONING:
Major Minor Patch
1 . 8 . 7

NODE.JS : Hello world
Hello.js
var http = require('http');
http.createServer(function(request, response) {
response.writeHead(200); //Status code in browser
response.write("Hello World.");//ResponseText
response.end();//Close the connection
}).listen(8080);//Listen for connection on this port
console.log('Listening on port 8080...');

• Run the server:
$ node Hello.js
(Listening on port 8080...)
• View output
$ curl http://localhost:8080
(Hello World)

Long Running Process
response.writeHead(200);
response.write(“Hello World running.");
response.end();
setTimeout(function() //Represent long running process
{
response.write(" Hello World is done.");
response.end();
}, 5000);
//5000ms = 5 seconds
}).listen(8080);

TWO CALLBACKS HERE
request
response.write(“Hello World running.");
response.end();
timeout
setTimeout(function() //Represent long running process
{
response.end();
}, 5000);
//5000ms = 5 seconds
}).listen(8080);

NOTE: TYPICAL BLOCKING THINGS
• Calls out to web services
• Reads/Writes on the Database
• Calls to extensions

EVENTS IN THE DOM
• The DOM triggers Events you can listen for
those events

EVENTS IN NODE 1
• Many objects in Node emit events

Also there is custom EventEmitter
var EventEmitter = require('events').EventEmitter;


http.createServer(function(request, response){ ... });

But what is really going on here?
http://nodejs.org/api/

Breaking It down

STREAMING RESPONSE
Readable stream

Writable stream

response.write(“Hello World Writing.");

setTimeout(function()
{
response.end();

}, 5000);
}).listen(8080);

Output to client:
Hello World Writing.
(5 seconds later)
Hello World is done.

$ curl -d 'hello' http://localhost:8080
Output on client: hello

READING AND WRITING A FILE
var fs = require('fs'); // require filesystem module
var file = fs.createReadStream("readme.md");
var newFile =
fs.createWriteStream("readme_copy.md");
require filesystem module
file.pipe(newFile);

UPLOAD A FILE
var fs = require('fs');
var newFile =
fs.createWriteStream("readme_copy.md");
request.on('end', function() {
response.end('uploaded!');
});
}).listen(8080);
On Client:
$ curl --upload-file readme.md http://localhost:8080
Output on client: uploaded!

DOCUMENTATION
http://nodejs.org/api/

REMEMBER THIS CODE 1?
var fs = require('fs');
var newFile = fs.createWriteStream("readme_copy.md");
http.createServer(function(request, response)
{
request.pipe(newFile);
request.on('end', function()
{
response.end('uploaded!');
});
}).listen(8080);

REMEMBER THIS CODE 2?
var newFile = fs.createWriteStream("readme_copy.md");
var fileBytes = request.headers['content-length'];
var uploadedBytes = 0;
request.pipe(newFile);
request.on('data', function(chunk)
{
uploadedBytes += chunk.length;
var progress = (uploadedBytes / fileBytes) * 100;
response.write("progress: " + parseInt(progress, 10) + "%n");
});
}).listen(8080);

References:
• IN T R O T O N O D E . J S (Authorized site)
• Ihrig C. J. - Pro Node.js for Developers
• Gackenheimer C. - Node.js Recipes

Thank You
• Any Suggestions and queries :
Website: http://prabinsilwal.com.np
Email: silwalprabin@hotmail.com

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