Node.js web-based Example :Run a local server in order to start using node.js in the browser and do server side tasks

Node.js
•Node.js is an open source server environment.
•Node.js allows you to run JavaScript on the
server.
•Node.js runs on various platforms (Windows,
Linux, Unix, Mac OS X, etc.)

Run a local server in order to
start using node.js in the
browser and do server side tasks

Getting Started
• Create a Node.js file named “Example.js", and add the following code:
• Create a Node.js file named “Example.js",
Example.js
var http = require('http');
http.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/html'});
res.end('Hello World!');
}).listen(8080);
node Example.js
Start your internet browser, and type in the address:
http://localhost:8080

var util = require("util");
res.end('Kongu IT World!');
}).listen(8080);
util.log("Server running at https://localhost:8080/");

Server.js
var fs=require('fs');
var myreadSt=fs.createReadStream('Sample.html');
myreadSt.pipe(res);
}).listen(8087);
Sample.html
<!DOCTYPE html>
<html>
<body>
<h1 style="color:blue;">A Blue
Heading</h1>
<p style="color:red;">A red
paragraph.</p>
</body>
</html>

Node.js fs.createReadStream() Method
• createReadStream() method is an inbuilt application programming
interface of fs module which allow you to open up a
file/stream and read the data present in it.
Syntax:
fs.createReadStream( path, options )
path: This parameter holds the path of the file where to read the file.
It can be string, buffer or URL.
options: It is an optional parameter that holds string or object.

// Node.js program to demonstrate the
// fs.createReadStream() method
// Include fs module
let fs = require('fs'),
// Use fs.createReadStream() method
// to read the file
reader = fs.createReadStream('input.txt');
// Read and display the file data on console
reader.on('data', function (chunk) {
console.log(chunk.toString());
});
How to show the data in the
console.log() ? (node.js)

• The data is a transfer from server to client for a particular request in the form of a stream.
• The stream contains chunks.
• A chunk is a fragment of the data that is sent by the client to server all chunks concepts to
each other to make a buffer of the stream then the buffer is converted into meaningful
data
Syntax:
request.on('eventName',callback)
• Parameters: This function accepts the following two parameters:
• eventName: It is the name of the event that fired
• callback: It is the Callback function i.e Event handler of the particular event.
• Return type: The return type of this method is void.
What is chunk in Node.js ?

Index.html / Client side
<html>
<head>
<title></title>
</head>
<body>
<form action="http://localhost:8087">
Enter n1:<input type="text" name="n1" value=""/><br>
Enter n2:<input type="text" name="n2" value=""/><br>
<input type="submit" value="Login"/>
</form>
</body>
</html>

http=require('http');
url=require('url');
querystring = require('querystring’);
function onRequest(req,res){
var path = url.parse(req.url).pathname;
var query =url.parse(req.url).query;
var no1 =querystring.parse(query)["n1"];
var no2=querystring.parse(query)["n2"];
var sum=parseInt(no1)+parseInt(no2);
console.log(sum);
res.write("The result is "+" " + sum);
res.end();
}
http.createServer(onRequest).listen(4001);
console.log('Server has Started.......');
Server.js/ Server
side

Node.js URL Module
• The URL module splits up a web address into readable parts.
• Parse an address with the url.parse() method, and it will return a URL
object with each part of the address as properties:

Node.js Query String Module
• The Query String module provides a way of parsing the URL query
string.
• Query String Methods
Method Description
escape() Returns an escaped querystring
parse() Parses the querystring and returns an object
stringify() Stringifies an object, and returns a query string
unescape() Returns an unescaped query string

Node.js web-based Example
• A node.js web application contains the following three parts:
1. Import required modules: The "require" directive is used to load a
Node.js module.
2. Create server: You have to establish a server which will listen to
client's request similar to Apache HTTP Server.
3. Read request and return response: Server created in the second
step will read HTTP request made by client which can be a browser
or console and return the response.

How to create node.js web applications
• Import required module: The first step is to use ?require? directive
to load http module and store returned HTTP instance into http
variable.
For example:
var http = require("http");

Create server:
• In the second step, you have to use created http instance and
• call http.createServer() method to create server instance and
• then bind it at port 8081 using listen method associated with server
instance.
• Pass it a function with request and response parameters and write
the sample implementation to return "Hello World".

Combine step1 and step2 together in a file
named "main.js".
http.createServer(function (request, response) {
// Send the HTTP header
// HTTP Status: 200 : OK
// Content Type: text/plain
response.writeHead(200, {'Content-Type': 'text/plain'});
// Send the response body as "Hello World"
response.end('Hello Worldn');
}).listen(8081);
// Console will print the message
console.log('Server running at http://127.0.0.1:8081/');

File: main.js
var http = require("http");
http.createServer(function (request, response) {
// Send the HTTP header
// HTTP Status: 200 : OK
// Content Type: text/plain
response.writeHead(200, {'Content-Type': 'text/plain'});
// Send the response body as "Hello World"
response.end('Hello Worldn');
}).listen(8081);
// Console will print the message
console.log('Server running at http://127.0.0.1:8081/');

node main.js Now server is started.

Make a request to Node.js server:
Open http://127.0.0.1:8081/ in any browser. You will see the following result.

Node.js File System (FS)
• Node File System (fs) module can be imported using following syntax:
Syntax:
var fs = require("fs")
The createReadStream() method is an inbuilt application programming interface of
fs module which allow you to open up a file/stream and read the data present in it.
Syntax:
fs.createReadStream( path, options )
path: This parameter holds the path of the file where to read the file. It can be
string, buffer or URL.
options: It is an optional parameter that holds string or object.

// Node.js program to demonstrate the
// fs.createReadStream() method
// Include fs module
let fs = require('fs'),
// Use fs.createReadStream() method
// to read the file
reader = fs.createReadStream('input.txt');
// Read and display the file data on console
reader.on('data', function (chunk) {
console.log(chunk.toString());
});

With html file
const http = require('http')
const fs = require('fs')
const server = http.createServer((req, res) => {
res.writeHead(200, { 'content-type': 'text/html' })
fs.createReadStream('index.html').pipe(res)
})
server.listen(process.env.PORT || 3000)

Node.js web-based Example :Run a local server in order to start using node.js in the browser and do server side tasks

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