NODE JS

Node.js is a platform built on Chrome's JavaScript run time for easily building fast and scalable network applications.

We can run javascript code on the server.


Why Node Js?
 Node.js operates on a single-thread, using non-blocking I/O calls, allowing it to support tens of thousands of  connections held in the event loop. and it also memory efficient.

Node Js Module 
Module in Node.js is a simple or complex functionality organized in single or multiple JavaScript files which can be reused throughout the Node.js application.

Type of module:
3 types module
a:File based module : we have export the file module like module.export and import that file module using required function.
b:Core module:Built in module ( its already in built)
c:External node module: node package manager (API) using npm commmand



Node REPL
REPL stands for Read-Eval-Print-Loop. It is a quick and easy way to test simple Node.js/JavaScript code.

# How to write hello world in node

How to exit node repl ?

=> Press 2 times Ctrl +C

How to install node js

Step 1 : Create a folder in drive using cmd promt

in that folder install node js , using cmd ==>  npm init

After Complete open folder in sublime text editor => package.json

Create index.js file  then create Hello World  

Run the Program in cmd  just write node and file name

# demo 1
 How to calculate area and perimeter 

  






out put 

# demo2 Find area and perimeter using File Based Module
    
    step1 : create new file  square.js ==> pest the code   using exports

    step2 : import the file in index.js  so we are using require

    step3: output ==> go to cmd and type node index