jumpstart-nodejs

What Is Node Js????.

• Node is a server-side platform.
• Built on Google Chrome's JavaScript Engine (V8 Engine).
• Uses an event-driven, non-blocking I/O model that makes it lightweight and efficient
• It runs on variuous platforms such as Windows, Linux, Unix & Mac OS X.

Features of Node.js

• Asynchronous - The server can respond to multiple requests at a time.It won’t stop or block any API request and will respond to all when the response is ready to send accordingly.
• Event Driven - The flow of the program is determined by events such as user actions thats mouse clicking.An event based system is always be in circular loop to execute it’s responsibilities.
• Single Threaded - All requests runs the same thread unlike Java/PHP/ASP.net based webservers every client request is instantiated on a new thread.

The main event loop is single-threaded but most of the I/O works run on separate threads, > because the I/O APIs in Node.js are asynchronous/non-blocking by design, in order to > accommodate the event loop.

• No Buffering − Node.js applications never buffer any data. These applications simply output the data in chunks.

Application of Node.js :

• I/O bound Applications
• Data Streaming Applications - online gaming, A financial institution tracks changes in the stock market in real time.
• Data Intensive Real-time Applications (DIRT).
• JSON APIs based Applications.
• Single Page Applications.

Other Uses of Node:

• It can be used as a scripting language to automate repetitive or error prone tasks on your PC.
• Write your own command line tool, such as Nodemon.
• Build cross-platform desktop apps.
• create your own robots.
• Blockchain.
• IOT.

Where Not to Use Node.js?

It is not advisable to use Node.js for CPU intensive applications. Since the main thread is blocked which means I need to create a separate JavaScript file and execute another node process on it.

Node.js Installation.

Ubuntu 16.04

$ sudo apt-get update
$ sudo apt-get install nodejs

Installation on Windows

 Use the MSI file and follow the prompts to install the Node.js. By default, the installer uses the      Node.js distribution in C:\Program Files\nodejs.

Check Installation

Node version

   $ nodejs -v

Hello World.

Create a file name hello.js and type the following code:

    console.log("Hello World!")

First web server

Create a file name server.js and type :

 const http = require('http'); //requiring Node’s native HTTP module.
 
 const hostname = "localhost";
 const port = 3000;  // Initializing server port.

 const server = http.createServer((req, res) => {    // new web server object.
    res.statusCode = 200;      // http status code.
    res.setHeader('Content-Type', 'text/plain');  // Type of response being emmitted .
    res.end('Hello World\n');  // What to diplayed .
  });

  server.listen(port, hostname, () => {
    console.log(`Server running at http://localhost:${port}/`);
  });

Save and start server on your terminal:

   $ nodejs server.js

Open up a browser and navigate to http://localhost:3000 to see “Hello, World!” displayed in the browser.

What the above code does:

We start by requiring Node’s native HTTP module and Initialize port server. We then use HTTP createServer method to create a new web server object, to which we pass an anonymous function. This function will be invoked for every new connection that is made to the server.

The anonymous function is called with two arguments (request(req) and response(res)) which contain the request from the user and the response, which we use to send back a 200 HTTP status code, along with our “Hello World!” message.

Finally, we tell the server to listen for incoming requests on port 3000, and output a message to the terminal to let us know it’s running.

Node Package Manager :

Wikipedia

npm is a package manager for the JavaScript programming language. It is the default package >manager for the JavaScript runtime environment Node.js.

Check version

    $ npm --version

To load dependencies we just have to run a command in command prompt:

  $ npm install 

If we want to install express js module :

  $ npm install express

Now you can use express in js file as follows:

 var express = require('express');

Package.json

After a npm install command package.json file is generated in the project root directory.It has the list of packages that your project depends on. Below is a sample of the package.json file:

 {
"name": "ApplicationName",
"version": "0.0.1",
"description": "Application Description",
"main": "server.js",
"scripts": {
  "start": "node server.js"
},
"repository": {
  "type": "git",
  "url": "https://github.com/npm/npm.git"
},
"dependencies": {
  "express": "~3.0.1",
  "sequelize":"latest",
  "q":"latest",
  "tedious":"latest",
  "angular":"latest",
  "angular-ui-router": "~0.2.11",
  "path":"latest",
  "dat-gui":"latest"
}

}