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Node.js Modules

 💥What is Modules?

A module encapsulates related code into a single unit of code. When creating a module, this can be interpreted as moving all related functions into a file.

 💥How to create Module

👉Create a module that returns the current date and time:

        👊exports.myDateTime = function () {
    return Date();
}; 

   👉Save the code above in a file called "firstmodule.js"

 👉Now we  can include and use the module in any of our Node.js files.

 

    👊 var http = require('http');
var dt = require('./myfirstmodule');
http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/html'});
    res.write("The date and time is currently: " + dt.myDateTime());
    res.end();
}).listen(8080);

 

 👉Save the code above in a file called "demo_module.js", and initiate the file

 

👉Initiate demo_module.js in Terminal

      C:\Users\Your Name> node demo_module.js 

 

👉 If we want result,We will use this path http://localhost:8080

💥 Node.js HTTP Module

      👉This allows Node.js to transfer data over the Hyper Text Transfer Protocol (HTTP).

         👊 var http = require('http');

//create a server object:
http.createServer(function (req, res) {
  res.write('Hello World!'); //write a response to the client
  res.end(); //end the response
}).listen(8080); //the server object listens on port 8080

     👉Save the code above in a file called "demo_http.js"

      👉then use below code in terminal

          C:\Users\Your Name>node demo_http.js

          
          👉 Then use port to open browser
                out put:
                          
                       Hello World!

 💥Node.js URL Module

👉Create two html files and save them in the same folder as your node.js files.

    👊var http = require('http');
var url = require('url');
var fs = require('fs');

http.createServer(function (req, res) {
  var q = url.parse(req.url, true);
  var filename = "." + q.pathname;
  fs.readFile(filename, function(err, data) {
    if (err) {
      res.writeHead(404, {'Content-Type': 'text/html'});
      return res.end("404 Not Found");
    } 
    res.writeHead(200, {'Content-Type': 'text/html'});
    res.write(data);
    return res.end();
  });
}).listen(8080); 

👉 node demo_fileserver.js 

👉http://localhost:8080/(htmlfilename)

Nodejs introduction

💥What is Node.js

😅 Node.js is an open source server framework
😅 Node.js is free
😅 Node.js runs on various platforms (Windows, Linux, Unix)
😅 Node.js uses JavaScript on the server

 💥What are the different between Node.js & PHP or ASP

       💦how is  PHP or ASP handles a file request

             😅Sends the task to the computer's file system.
             😅Waits while the file system opens and reads the file.
             😅Returns the content to the client.
             😅Ready to handle the next request.



      💦how is Node.js handles a file request
 
            😅Sends the task to the computer's file system.
            😅Ready to handle the next request.
            😅When the file system has opened and read the file, the server returns the content to the client.

💥What are the functions in Node.js?

    😅Node.js can generate dynamic page content
    😅Node.js can create, open, read, write, delete, and close files on the server
   😅Node.js can collect form data
   😅Node.js can add, delete, modify data in your database

💥 Node.js files have extension ".js"

Mongo db Install

💥 How to install Mongodb

      💢 Start MongoDB

                     👀 sudo service mongodb start

       💢 Stop MongoDB

                    👀 sudo service mongodb stop

          💢 Restart MongoDB

                     👀 sudo service mongodb restart

  💥 To use MongoDB run the following command.

                       👀 mongo

  💥How to create database

            💧If you want to create a database with name <mydb>, then use database statement would be as follows 

>use mydb
switched to db mydb

           💧To check your currently selected database, use the command db

>db
mydb

            💧If you want to check your databases list, use the command show dbs.

>show dbs
local     0.78125GB
test      0.23012GB

           💧Your created database (mydb) is not present in list. To display database, you need to insert at least one document into it.

>db.student.insert({"name":"Abi"})
>show dbs
local      0.78125GB
mydb       0.23012GB
test       0.23012GB

  💥 How to drop Database

Basic syntax of dropDatabase() command is as follows −
💥db.dropDatabase() 

          💧This will delete the selected database. If you have not selected any database, then it will delete default 'test' database.


     👉First, check the list of available databases by using the command, show dbs.

      💧>show dbs
 local 0.78125GB 
mydb 0.23012GB 
 test 0.23012GB 
 
      👉If you want to delete new database <mydb>, then dropDatabase() command would be as follows 

    💧>use mydb switched to db mydb  
     > db.dropDatabase() 
     >{ "dropped" : "mydb", "ok" : 1 } >
 
       👉Now check list of databases.

>show dbs 
 local 0.78125GB 
test 0.23012GB >

MongoDB

            💥 MongoDB is an open-source document database and leading NoSQL database

            💥 MongoDB is a cross-platform, document oriented database that provides, high performance, high availability, and easy scalability. MongoDB works on concept of collection and document.

💥 Advantages of MongoDB over RDBMS

• Schema less − MongoDB is a document database in which one collection holds different documents. Number of fields, content and size of the document can differ from one document to another.
  
• Structure of a single object is clear.
  
• No complex joins.
  
• Deep query-ability. MongoDB supports dynamic queries on documents using a document-based query language that's nearly as powerful as SQL.
  
• Tuning.
  
• Ease of scale-out − MongoDB is easy to scale.
  
• Conversion/mapping of application objects to database objects not needed.
  
• Uses internal memory for storing the (windowed) working set, enabling faster access of data.
  
  
  

  💥 Why Use MongoDB?

• Document Oriented Storage − Data is stored in the form of JSON style documents.
  
• Index on any attribute
  
• Replication and high availability
  
• Auto-sharding
  
• Rich queries
  
• Fast in-place updates
  
• Professional support by MongoDB

 💥 Where to Use MongoDB?

• Big Data

• Content Management and Delivery

• Mobile and Social Infrastructure

• User Data Management

• Data Hub

jQuery Event

   💥 All the different visitor's actions that a web page can respond to are called events.

  💥  An event represents the precise moment when something happens.
Examples:

• moving a mouse over an element

            💧<script>
$(document).ready(function(){
    $("p").on({
        mouseenter: function(){
            $(this).css("background-color", "lightgray");
        }, 
        mouseleave: function(){
            $(this).css("background-color", "lightblue");
        },
        click: function(){
            $(this).css("background-color", "yellow");
        } 
    });
});
</script>

• selecting a radio button

           💧<script>
$(document).ready(function(){
    $("input").keypress(function(){
        $(this).hide();
    });
});
</script>

• clicking on an element

•        💧<script>
  $(document).ready(function(){
      $("p").on("click", function(){
          $(this).hide();
      });
  });
  </script>

jQuery

💥 jQuery is a JavaScript Library.

💥  jQuery greatly simplifies JavaScript programming.  
💥 The purpose of jQuery is to make it much easier to use JavaScript on your website.

💦 jQuery Syntax

Basic syntax is: $(selector).action()

• A $ sign to define/access jQuery
• A (selector) to "query (or find)" HTML elements
• A jQuery action() to be performed on the element(s)

 
 

💦 jQuery Selectors

      👦The element Selector

              You can select all <p> elements on a page like this:

$("p") 

 

 

    👦The  #id selector

      An id should be unique within a page, so you should use the #id selector when you want to find a single, unique element.

$("#test") 

 

     👦 The . class selector

     To find elements with a specific class, write a period character, followed by the name of the class:

$(".test")