Node_text.txt

What is Server Side Scripting?
Various Server Side Scripting Technologies

                                Node.js

- It is a server side script technology that run on V8 compiler.
- It is JavaScript Based
- It uses Async techniques
- No Buffering
- It sends data in form of packet.
- It is single threaded
- Not good for CPU intensive apps.
- It is faster as it is single threaded.
- Not good for ERP.
- Good for audio and video streaming apps.

# Setup Environment for Node.js

1. Download and Install Node.js

2. Test >node -v >npm -v

# Server Side Objects

1. Request
2. Response
3. Session
4. Application
5. Cookie
6. OS
7. FS
8. Server
9. Memory Stream

# Server Side Techniques

1. Model Binding
2. Data Binding
3. Routing
4. Security
5. Buffering

# Language

1. JavaScript

Note: JavaScript is used only for REPL and Language Features.
No DOM manipulations.

        R        - Read
        E        - Evaluate [Expressions]
        P        - Print
        L        - Loop

         document.write()        // invalid
         alert()
         prompt()
         innerHTML etc..

# Node REPL Terminal:

- It provides a terminal to run node.js commands
- You can also run REPL.
- To open REPL terminal

        C:\> node
        >

# Node.js Programs

- Every node.js program is a JavaScript program stored in ".js" file.
- You can compile and run by using node compiler.

Ex:
hello.js
console.log("Hello ! Node.js");

C:\> node hello.js

# Node.js Server Side Program Structure:

1.  Download and Install every module that your want to use in application.
    [ Node.js comes with only core module - others you have to download ]

2.  Import module into program by using "require()".

        var  refName = require("ModuleName");
        refName.Class
                 refName.function()
                 refName.property

3.  Implement the classes and functions to define a functionality.

                  Node  FS Module
                  =============

- Node "File Stream" module provides a set of properties and methods that are used to access and control files on server.

1.  Install FS module in your project

        > npm install fs --save

2.  Write the following program
    "index.js"

var fs = require("fs");

console.log("Read Started");
var data = fs.readFileSync("../data/help.txt");
console.log(data.toString());
console.log("Read Completed");

              > node index.js

Note: Node.js is using synchronous technique for executing the tasks.

Ex: Async Reading

var fs = require("fs");

console.log("Read Started");

fs.readFile("../data/help.txt", function(err, data){
if(!err){
console.log(data.toString());
} else {
console.log(err);
}
})

console.log("Read Completed");

                                Node  OS Module
                            =======================

- It provides a set of properties and methods that are used by server to access the information about OS running on Server.

cpus() It returns the CPU structure.
Syntax:
var os = require("os");
console.log(os.cpus());

freemem Free memory

totalmem Total memory

Ex:
var os = require("os");
console.log(` Free Memory : ${os.freemem} \n Total : ${os.totalmem}`);