𝐏𝐒𝐂𝐨𝐝𝐞𝐫

MongoDB is an open source cross-platform document-oriented database program. Classified as a NoSQL database program, MongoDB uses JSON-like documents with optional schemas

Aggregation Pipeline

An aggregation pipeline consists of one or more stages that process documents:

Each stage performs an operation on the input documents. For example, a stage can filter documents, group documents, and calculate values.
The output from a stage are passed to the next stage.
An aggregation pipeline can return results for groups of documents. For example, return the total, average, maximum, and minimum values

Complete Aggregation Pipeline Examples

db.orders.insertMany( [
{ _id: 0, name: "Pepperoni", size: "small", price: 19,
quantity: 10, date: ISODate( "2021-03-13T08:14:30Z" ) },
{ _id: 1, name: "Pepperoni", size: "medium", price: 20,
quantity: 20, date : ISODate( "2021-03-13T09:13:24Z" ) },
{ _id: 2, name: "Pepperoni", size: "large", price: 21,
quantity: 30, date : ISODate( "2021-03-17T09:22:12Z" ) },
{ _id: 3, name: "Cheese", size: "small", price: 12,
quantity: 15, date : ISODate( "2021-03-13T11:21:39.736Z" ) },
{ _id: 4, name: "Cheese", size: "medium", price: 13,
quantity:50, date : ISODate( "2022-01-12T21:23:13.331Z" ) },
{ _id: 5, name: "Cheese", size: "large", price: 14,
quantity: 10, date : ISODate( "2022-01-12T05:08:13Z" ) },
{ _id: 6, name: "Vegan", size: "small", price: 17,
quantity: 10, date : ISODate( "2021-01-13T05:08:13Z" ) },
{ _id: 7, name: "Vegan", size: "medium", price: 18,
quantity: 10, date : ISODate( "2021-01-13T05:10:13Z" ) }
] )

Calculate Total Order Quantity

db.orders.aggregate( [
// Stage 1: Filter pizza order documents by pizza size
{
$match: { size: "medium" }
},
// Stage 2: Group remaining documents by pizza name and calculate total quantity
{
$group: { _id: "$name", totalQuantity: { $sum: "$quantity" } }
}
] )

Javascript

First what do you mean 'Javascript'

In simple words 'Every thing is javascript happen inside an Execution Context and it is lightweight,interpreted(means "it will execute the code line wise ") programming language.'

javascript is client slide scripted language

javascript is most popular language now day,

Why Study Javascript?

Javascript is used in web-development and extend to mobile app development ,desktop app development and game development
Every thing in javascript comes installed on every modern web browser('like :google chrome,safari) and not need any environment setup

Let the terms of javascript :

Execution Context(the environment in which our code is executed and is evaluted)
Execution Stack

Execution Context

Javascript engine creates the global execution context before it start to execute any code

NOTE: Global Execution context lies inside the Execution Context

Execution context has three properties

variable object
scope chain
'this' variable

Variable and function that is not inside any function .A new Execution Context get created every time

a function is executed

The global execution context just like any other execution context ,except that it get created by default

It is associated with global object Which means a window object

Example : this===window,name == window.name

Execution Stack

Execution stack also known as 'calling stack' is a stack follow 'LIFO'(last in first out) Structure

which is used to store all the execution context created during the code execution

Every code that is present inside the blue container which will contained in execution context and when function call it will gonna store in Execution stack (like you call function a() and it is stored in stack (orange in color in image) same like this all function call line wise and stored in stack and when calling competed that function will remove from calling stack

Variable object

For each function (function declaration ) a property is created in the varible object .which is pointing to that function

for each varible (variable declaration ) a property is created in the variable object which is the set to undefined

Hoisting is a javascript mechanism where variable and function declarations are moved to the top of

their scope before the code execution

Function Hoisting

Before the execution phase every variable and funtion moved to top of their global scope and set variable value to 'undefined ' and in case of function it store the all function definition

CODE:

console.log(fun())

console.log(x)

var x=10

function fun(){

console.log('printing function')

}

OUT-PUT on Browser:

undefined
f fun(){`

console.log('printing function')

}

Lexical Environment :

it's the internal js engine construct that holds identifier-variable mapping. (here identifier refers to the name of variables/functions, and variable is the reference to actual object [including function type object] or primitive value). A lexical environment also holds a reference to a parent lexical environment.

In simple words (local memory + parent lexical Environment ) this both shows the lexical environment of current execution context

And every lexical environment tracks its parent lexical environment (that of parent execution context)

As a result, every function has a chain of lexical environments attached to it.

Scope : it's the language agnostic concept, to refer to the visibility of variables or functions to the executing code.

In js a variable or function is visible to the executing code, if it is there in the current lexical environment or in the lexical-environment-chain of the enclosing function. In case of global code, the chain does not exist.

Regarding Let and Const

'Let' and 'Const' declarations are both block-scoped, which means they are only accessible within the { } surrounding them "var', on the other hand, doesn't have this restriction.

TEMPORAL DEAD ZONE

This term is describing the state where variables are un-reachable. They are in scope, but they aren't declared.

Temporal dead zone : time between the initiation of variable and assigning value to variable is known as temporal dead zone

CODE:

1:{ console.log(money)// This is the temporal dead zone for the money variable

let money= 25 ; // now temporal dead zone no more

console.log(money)

}

2:{ console.log(a)

let a=12; /// we can't use same name of variable name with once it is defined to 'let '

var a=12;

}

Here you can find Reference error in both the cases

coming very soon

LINUX COMMAND

pwd command

Use the pwd command to find out the path of the current working directory (folder) you’re in. The command will return an absolute (full) path, which is basically a path of all the directories that starts with a forward slash (/). An example of an absolute path is /home/username.

cd command

Let’s say you’re in /home/username/Documents and you want to go to Photos, a subdirectory of Documents. To do so, simply type the following command: cd Photos

There are some shortcuts to help you navigate quickly:

cd .. (with two dots) to move one directory up cd to go straight to

the home folder cd- (with a hyphen) to move to your previous directory

ls command

If you want to see the content of other directories, type ls and then the directory’s path. For example, enter ls /home/username/Documents to view the content of Documents

There are variations you can use with the ls command:

ls -R will list all the files in the sub-directories as well
ls -a will show the hidden files
ls -al will list the files and directories with detailed information like the permissions, size, owner, etc.

cat command

It is used to list the contents of a file on the standard output (sdout);

cat filename creates a new file
cat filename1 filename2 filename3 joins two files (1 and 2) and stores the output of them in a new file (3)
to convert a file to upper or lower case use, cat filename | tr a-z A-Z output.txt

mv command
The arguments in mv are similar to the cp command. You need to type mv, the file’s name, and the destination’s directory. For example: mv file.txt /home/username/Documents.

To rename files, the Linux command is mv oldname.ext newname.ext

mkdir command

Use mkdir command to make a new directory — if you type mkdir Music it will create a directory called Music.

To generate a new directory inside another directory, use this Linux basic command mkdir Music/Newfile use the p (parents) option to create a directory in between two existing directories. For example, mkdir -p Music/2020/Newfile will create the new “2020” file.

rmdir command

you need to delete a directory, use the rmdir command. However, rmdir only allows you to delete empty directories

rm command

The rm command is used to delete directories and the contents within them. If you only want to delete the directory — as an alternative to rmdir — use rm -r.

touch command

The touch command allows you to create a blank new file through the Linux command line. As an example, enter touch /home/username/Documents/Web.html to create an HTML file entitled Web under the Documents directory.

find command

using find also searches for files and directorie

sudo command

“SuperUser Do”, this command enables you to perform tasks that require administrative or root permissions. However, it is not advisable to use this command for daily use because it might be easy for an error to occur if you did something wrong.

df command

Use df command to get a report on the system’s disk space usage, shown in percentage and KBs. If you want to see the report in megabytes, type df -m.

du command

If you want to check how much space a file or a directory takes, the du (Disk Usage) command is the answer

If you want to see it in bytes, kilobytes, and megabytes, add the -h argument to the command line

head command

The head command is used to view the first lines of any text file.

By default, it will show the first ten lines, but you can change this number to your liking. For example, if you only want to show the first five lines, type head -n 5 filename.ext.

tail command

This one has a similar function to the head command, but instead of showing the first lines, the tail command will display the last ten lines of a text file. For example, tail -n filename.ext.

diff command

the diff command compares the contents of two files line by line. After analyzing the files, it will output the lines that do not match.

tar command

The tar command is the most used command to archive multiple files into a tarball — a common Linux file format that is similar to zip format, with compression being optional.

chmod command

chmod is another Linux command, used to change the read, write, and execute permissions of files and directories.

chown command

The chown command enables you to change or transfer the ownership of a file to the specified username. For instance, chown linuxuser2 file.ext will make linuxuser2 as the owner of the file.ext.

ping command

the ping command to check your connectivity status to a server. For example, by simply entering ping google.com, the command will check whether you’re able to connect to Google and also measure the response time.

wget command

The Linux command line is super useful — you can even download files from the internet with the help of the wget command. To do so, simply type wget followed by the download link

history command

When you’ve been using Linux for a certain period of time, you’ll quickly notice that you can run hundreds of commands every day. As such, running history command is particularly useful if you want to review the commands you’ve entered before.

echo command

This command is used to move some data into a file. For example, if you want to add the text, “Hello, my name is John” into a file called name.txt, you would type echo Hello, my name is John name.txt

cp command

the cp command to copy files from the current directory to a different directory.

the command cp scenery.jpg /home/username/Pictures would create a copy of scenery.jpg (from your current directory) into the Pictures directory

React JS

HEY GUYS WELCOME

I have explained every and each steps to install React in your local pc ,It will help you to resolve your problem that you are tackling/facing during its installation.

LETS KNOW FIRST WHAT IS REACT JS

React JS is a open source to Javascript Library is used to create dynamic and interactive user interface for mobile and web application.

In short points

highly flexible
scalable
fast front-end for web & mobile applications

KNOWLEDGE REQUIRED FOR REACT JS:

HTM
CSS
JAVASCRIPT
NODE AND NPM

"Very crucial information ,Here we are using virtual DOM instead of Real DOM"

"In React JS every application UI is broken into Component ,that makes easy to handle"

Formate of file Naming =>filename with capital letter then dot jsx ( first.jsx )

JSX( Javascript Syntax Extension)

DATA FLOW UNIDIRECTION

React JS follows one-way data binding or unidirectional data flow that gives better control throughout the application.

# React JS Installation part #

Carefully trash every step of installation of react js in your local pc

Install Visual Studio Code

Download and install Visual Studio Code from the following

URL =>https://code.visualstudio.com/download

step 1: open browser and write node install

download from official node js website

website link : https://nodejs.org

Once Completed then check the version

Install Create-React-App Tool

step 2: Run the given below command in your laptop powershell

=> npm install -g create-react-app

Creating a new react project

step 3: after the completion of step 2, Create project and application in C:\

Let's create a new Project now using the command.

=> create-react-app test-project

you folder structure will resemble with this

Running the React Application

the Project we have created and run it locally on our system using npm start. Launch the browser and visit http://localhost:3000. We can then see our first React Application running in the browser.

step4: cd test-project

npm start

React animation will appear in browser

if you has followed the steps of installation correctly ,by chance you are facing any problem then once repeat /read the steps of installation carefully.

Let's initiate the web project ,first of we are gonna to make amazing single page website,

Modules required:

npm
create-react-app
styled-components
react-router-dom

first we check npm installed perfectly

write this command on terminal :

node -v

Installation in done :

Every Thing is now done perfectly so we are gonna make navbar ,

we’ll only need to install the React Router library to help us switch views of the HOME in our app when we click on the HOME on the links.

npm install react-router-dom

First, we’ll build the navbar itself. To do that, we’ll create a file named Navbar.js in src/component

import React from 'react';
import {  Link } from "react-router-dom";
const Navbar= () =>{
  return (
  <div>
    <li>
      <Link to="/">Home
     </Link>
    </li>
    <li>
      <Link to="/contact">contact
     </Link>
    </li>
    <li>
      <Link to="/service">service
      </Link>
    </li>
    <li>
      <Link to="/detail">Detail
     </Link>
    </li>
  </div>
  );
}
export default Navbar;

We have to import Link from the react-router-dom library we’ve already installed. <Link> comes out of the box from the React Router library to allow us to navigate to the exact route name in the to attribute. What it does is convert whatever’s inside the attribute (text, images, etc.) into a link. When you click it, you are taken to the route that’s already indicated in the to attribute.

NOW WE ARE GONNA MADE THE INDIVIDUAL " to " ATTRIBUTE LINK

now we are creating each page for each "to" attribute (for '/' ,'/Contact', '/Service' ,'/Detail').

We’ll place them in src/pages/navbar, like so:

>>>>>>page for '/'<<<<<<<<<

import React from 'react';
const Home = () =>{
  return (
    <div>
      <h3>HOME</h3>
    </div>
  );
}
export default Home;

>>>>>>page for '/Contact'<<<<<<<<<

import React from 'react';
const Contact = () =>{
  return (
    <div>
      <h3>Contact</h3>
    </div>
  );
}
export default Contact;

>>>>>>page for '/Service'<<<<<<<<<

import React from 'react';
const Service = () =>{
  return (
    <div>
      <h3>Service</h3>
    </div>
  );
}
export default Service;

>>>>>>page for '/Detail'<<<<<<<<<

import React from 'react';
const Detail= () =>{
  return (
    <div>
      <h3>Detail</h3>
    </div>
  );
}
export default Detail;

Now, go into your App.js, and import react-router-dom into your project:

import { Route, Switch } from 'react-route'
import navbar from "./components/navbar"
import Home from "./pages/Home"
import Contact from "./pages/Contact"
import Service from "./pages/Service"
import Detail from "./pages/Detail"
function App() {
  return (
 <Router>
  <navbar />
  <Switch>
   <Route path='/' exact component={Home} />
   <Route path='/Contact' component={Contact} />
   <Route path='/Service' component={Service} />
   <Route path='/Detail' component={Detail} />
  </Switch>
</Router>
  );
}

export default App

Congratualations Guys You have learned How to make Navbar using Link , Router and Switch

𝐏𝐒𝐂𝐨𝐝𝐞𝐫

Hello,

𝐈 𝐚𝐦 𝐩𝐫𝐚𝐬𝐡𝐚𝐧𝐭 𝐬𝐫𝐢𝐯𝐚𝐬𝐭𝐚𝐯𝐚

More Info About Me

Prashant Srivastava

20 march 2001

Kapashera, New Delhi

prashantsrivastava5116@gmail.com

+91 7827677523

Web Design(React Js)

BlockChain

Rative App

C++

My Resume

EXPERIENCE

EDUCATION

web developer

....student

Dronacharya Collage of Engineering University

Rao Ganga Ram Public School

High School from Rao Ganga Ram Public School

2

Happy Clients

10

Complete Projects

2000

Lines of Codes

0

Awards Received

..Skill..

Ethereum

Web3js

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HTML/CSS

JavaScript

PYHTON

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Martin Luther King Jr

Portfolio

MongoDB

Aggregation Pipeline

Complete Aggregation Pipeline Examples

Calculate Total Order Quantity

Crystal-Clear-Javascript

Next js tutorial

Linux command Line

cat command

It is used to list the contents of a file on the standard output (sdout);

mv commandThe arguments in mv are similar to the cp command. You need to type mv, the file’s name, and the destination’s directory. For example: mv file.txt /home/username/Documents.

To rename files, the Linux command is mv oldname.ext newname.ext

rmdir command

rm command

touch command

find command

sudo command

df command

du command

head command

The head command is used to view the first lines of any text file.

tail command

diff command

tar command

chmod command

chown command

ping command

wget command

history command

echo command

cp command

the cp command to copy files from the current directory to a different directory.

React js

Popular Posts

Let's work together !

I am available for working on projects.

Get In Touch

Phone : 7827677523

Address : kapashera New Delhi 11037

Email : prashantsrivastava@gmail.com

mv command
The arguments in mv are similar to the cp command. You need to type mv, the file’s name, and the destination’s directory. For example: mv file.txt /home/username/Documents.

Phone :
7827677523

Address :
kapashera New Delhi
11037

Email :
prashantsrivastava@gmail.com