DEV Community: mohandass

Discuss about the topics of 1.what is callback function in js 2.Javascript is single threaded or multithreaded ? 3. Array iteration methods in js

mohandass — Tue, 14 Apr 2026 10:01:26 +0000

A callback function in javascript is a function passed as an argument into another function.
Which is then executed or (callback) inside that outer function to complete the specific task.
Later is typically when a specific event occurs or an asynchronous operation completes.

BASIC CALLBACK:

OUTPUT:
Hello, thomas
Goodbye

Types of Callback

There are two primary ways callback are used:

Asynchronous callback
Synchronous callback

ASYNCHRONOUS

Asynchronous callback is executed immediately during the execution of the main function,blocking further code until finish.

Example:Array.Prototype.forEach(),map(),and filter()-(TBD)

SYNCHRONOUS

Synchronous callback is executed at a later time after an operation like fetching data or a time.Completes allowing the rest of the program to continue running in meantime.

Examples: setTimeout(), addEventListener(), and network requests (API calls)-(TBD)

Javascript is single threaded or Multithreaded

Javacsript is a single-threaded meaning it executes one task at a time on a single main thread.While the language itself dose not support multi threads for execution it achieves concurrency doing many things at once through an event-driven,non-blocking architecture.

Array Iteration Methods in javascript

A javascript in array iteration methods are built in tools that allow you to loop through array elements and perform operations on them.These methods typically take a callback function as a argument which is executed for each items in the array.

Array forEach
Array map()
Array flatMap()
Array filter()
Array reduce()
Array reduceRight()
Array every()
Array some()
Array from()
Array keys()
Array entries()
Array with()
Array Spread (...)
Array Rest (...) - (TBD)

1. forEach

The forEach() method calls a function (a callback function) once for each array element.It's used for side effects, and returns undefined.

Example:

Note that the function takes 3 arguments

The item value
The item index
The array itself

Above the example used the value and index parameters only.

OUTPUT:
50 0
30 1
25 2
10 3
60 4

WHAT IS FTP,TCP

mohandass — Sat, 11 Apr 2026 18:09:27 +0000

1. File Transfer Protocol(FTP)

File transfer protocol(FTP) is an application layer protocol that Used to file transfer between client and a server over a TCP,IP Network.It's provide a standardized method for file exchange across Different system.
- Support text,image,binary,and program files.
- Enable uploading,downloading,and remote file management.
- Used to TCP for ensure reliable communication.

Working and Uses of FTP

FTP follows a client-server model and uses two connections
Control connection (port 21) for commends.
Data connection(port 20)for file transfer.
User connect to the server use login credentials.
User navigate directories used commends ls and cd.
Using for transferring files uses get and put.
supports both active and passive mods for communication.


         control channel 
client -------------------> sever 
       <------------------                     
           Data channel

Types of Connection in FTP

FTP use two separate TCP connection to handle communication one dedicating to control information and another dedicating to actual data transfer
Control connection
data connection

FTP Data Types

FTP data types define how file contents are represented and transmitted between the client and server during file transfer.

ASCII: This data type is used for transferring text files with character encoding based on the ASCII standard.
EBCDIC: This data type is used for transferring text files encoded in IBM’s Extended Binary Coded Decimal Interchange Code.
Image (Binary): This data type transfers files as a continuous stream of bytes without any modification.
Local: This data type is used for transferring files that contain data stored in logical bytes of a specified bit length.

FTP common commends

get filename - download a single file in the server.
mget filename - download a multiple files form the server.
ls - used for list of the files in the current server directory.

Types of FTP

Anonymous FTP
Password-Protected FTP
FTPS (FTP Secure)
SFTP (SSH File Transfer Protocol)
(TBD)

2. Transmission control protocol(TCP)

Transmission control protocol is the protocol that allow the device communicate reliable a network.It is ensure that data reaches the destination correctly and a right order.Even the part of the network slow and unreliable.

It works at the Transport Layer (Layer 4) of the OSI model and is an essential part of the TCP/IP protocol suite used for Internet communication.
TCP establishes a logical connection between the sender and receiver before data transmission begins.
It ensures that data is delivered accurately and in the same order in which it was sent using acknowledgements and sequence numbers.
TCP detects errors using checksums and retransmits lost or corrupted packets to maintain data integrity.
It controls the data transmission rate to avoid overwhelming the receiver and adapts to network congestion for efficient communication.

Connection Establishment (Three-Way Handshake)

TCP is connection-orientated, meaning a connection must be established before any data is sent. This is done using a three-way handshake

TCP Handshake process

           FIN-ACK
       -------------->
             ACK
       <------------- 
           ACK-FIN
 Client<--------------Server  
             ACK
      --------------->

Step 1: FIN (Client → Server): The client sends a FIN segment to initiate closure, entering the FIN-WAIT-1 state.

Step 2: ACK (Server → Client): The server sends an ACK to acknowledge the FIN. The server enters CLOSE-WAIT (can still send data), and the client enters FIN-WAIT-2.

Step 3: FIN (Server → Client): Once the server finishes sending remaining data, it sends its own FIN segment to the client.

Step 4: ACK (Client → Server): The client sends an ACK to acknowledge the server's FIN, entering the TIME-WAIT state. After a set period, the connection is fully closed.

WORKING

Segmenting
Routing via IP
Reassembly at Receiver
Acknowledgments (ACKs)
Retransmission
Flow & Error Control
(TBD)

REFERENCE:https://www.geeksforgeeks.org/

Discuss about the topics of 1.what is javascript 2.Comparison of data types in js 3.Different Between Primitive and Non-primitive

mohandass — Thu, 09 Apr 2026 19:14:15 +0000

what is javascript

Javascript is the high level,interpreted language that sever is the One of the core technologies of the world wide web.
- Used to create Interactive and dynamic content for websites. While HTML provides the Structure of a page and CSS handled the style.
Javascript can ,calculate,mainpulat,and validate data.
Javascript is an object-oriented programing(OOP)language.But it is unique because it is prototype based rather than class based like (java,c++).
JavaScript is both a scripting language and a programming language.While it originated as a lightweight scripting tool for web browsers, it has evolved into a full-fledged, high-level programming language used for complex applications across many platforms.
Javascript is provides The behavior what make things on the page move,react or update to Your click.

Comparison of data types in javascript

In javascript data types are broadly categorized into "primitive" and "non-primitive"(reference) types.The fundamental difference lies in how they are stored in memory and how they behave during assignment or modifying.

Primitive Data Types

Primitive data types are the built-in data types provide by a javascript.They represent single values and are not mutable. JavaScript supports the following primitive data types
string
number
boolean
null
undefined
bigInt
symbol

String

The string data type is used to represent a sequence of characters that are surrounding by a single or double quotes

Example:"hello",'welcome'

2.Number

A number data type is used to integers and floating point numbers

Example:(10,5,25)

Boolean

it's logical values either true or false

null

The null is intentional absence any value

undefined

The undefined is variables declared but assigned a value

Bigint

It's used for very larger integer and number type

Example:(9007199254740991n)

symbol

It's used for unique identifiers in object properties

Non-primitive data types

The non-primitive data types are complex data structure that can store collection of value or more complicate entities.
object
Array
Function

Object

The object is collect a key value pairs used to store data
It's used to curly bracket {}
example:

Array

The array is used to multiple values in single container
It's use with square bracket []

Example:

Function

The function is used to reusable block of code designed to perform a task.

Example:

Different Between primitive and Non-primitive Data Types

Primitive data type:

*immutable their values can not be changed once created

It's mean the immutable is reassign the values dose not replace a memory in older one.Then create the new memory to stored the values

let i = 10;
i = 20;

Storage

Stored the values directly in the stack
Every values stored the stack in line by line
FILO - first in last out

Comparison

compared by a actual value

Example:

Methods

Do not have any builtin methods but use the wrappers

Non-primitive Data Types

mutable The content can be changed or modified after creation

Storage: Stored by the heap

Dose not maintaining any order stored by the heap

Comparison

Compared by memory reference or address

Example:

REFERENCE :
https://www.w3schools.com/js/js_datatypes.asp

https://www.geeksforgeeks.org/javascript/primitive-and-non-primitive-data-types-in-javascript/

Array basic methods in j.s

mohandass — Wed, 08 Apr 2026 21:42:26 +0000

In javascript,array methods are built in the functions that help you add,remove,or manipulate elements in the array.

1. Array length

The length is property that tells you how many elements are in an array.

EXAMPLE:

Inside the array have a 4 elements.So the size of length is 4.

OUTPUT:
4

2. Array toString()

The toString() array method that coverets an array an array into a comma separated string.

EXAMPLE:

The toString method is join all elements into a string separate
a comma.
this method dose not change the original array.

OUTPUT:
BMW,TATA,BENZ,VOLVO

3. Array at()

The at() method is used to access an elements in array using its indexed.

EXAMPLE:

The carbrand.at(2) returns an indexed element 2 is the "BENZ"
Dose not modify the array.

OUTPUT:
BENZ

4. Array join()

The join() method is used to covert an array into a string it's join all elements with a specified separator.
It's behaves just like toString().

EXAMPLE:

It this join() array method we gives the ( - ).so it's create a array into a string joins with inbetween (-) all elements.
The original array stays unchanged.

OUTPUT:
BMW-TATA-BENZ-VOLVO

5. Array pop()

The pop() is used to remove the last elements from a array and it's return that elements.

EXAMPLE:

This pop() method is remove the array last elements "VOLVO"
it's modified the original array.

OUTPUT:
[ 'BMW', 'TATA', 'BENZ' ]

6. Array push()

The push() method is used to add one or more elements in end of the array.

EXAMPLE:

This push() method add element "AUDI" to the end an array.
It is also modified the original array and new length of the array.

OUTPUT:
[ 'BMW', 'TATA', 'BENZ', 'VOLVO', 'AUDI' ]

7. Array shift()

The shift() array method is used to remove the first elements from the array and return that all other elements to string index.

EXAMPLE:

This shift() method is remove the first element "BMW" and then remaining element are shift into the place of removed element.
This method is changed the original array.

OUTPUT:
[ 'TATA', 'BENZ', 'VOLVO' ]

8. Array unshift()

The Array unshift() is used to add one or more elements to the starting from the array.

EXAMPLE:

This unshift() method is add "MG" elements beginning the array.
It's changed the original array and return the new length of the array.

OUTPUT:
[ 'MG', 'BMW', 'TATA', 'BENZ', 'VOLVO' ]

9. Array.isArray()

The Array.isArray() method is used to check whatever a value is an array it's return the true and false otherwish it's not a array.

EXAMPLE:

If the carbrand is array.so the return is "true".

OUTPUT:
true

10. Array delete()

The Array delete() method is used leaves undefined holes in the array.
If you the pop() or shift() method instead of delete.

EXAMPLE:

Use delete method to remove the mentioned value.But another elements are not shift the array.
The array length is not changed.

OUTPUT:
[ 'BMW', <1 empty item>, 'BENZ', 'VOLVO' ]

11. Array concat()

The concat() is used to merge two or more array into the new array without changing the original array

EXAMPLE:

The concat method merge the carbrand2 array and carbrand1 array in a combine with order for all values
The original array dose not changed

OUTPUT:

[ "BMW", "TATA", "BENZ", "VOLVO", "AUDI", "HONDA", "TOYOTA", "KIA" ]

12. copyWithin()

The copyWithin() method used to copy the part of array elements to the another location in the same array

EXAMPLE:

OUTPUT:
[ 'BMW', 'TATA', 'BENZ', 'TATA' ]

13. Array flat()

A Array flat() method is used create a new array where sub-array elements are marge with main array

EXAMPLE:

OUTPUT:

[ 'BMW', 'TATA', 'BENZ', 'VOLVO' ]

14. Array slice()

The slice() method is slice out a piece of array into a new array

EXAMPLE:

Return a new array
It's not changed the original array

OUTPUT:
[ 'BMW', 'TATA' ]

15. Array splice()

The splice() method is used to add,remove,or replace elements in an array

EXAMPLES:

removing elements

Adding elements

Replace elements

16. Array toSpliced()

EXAMPLE:

Constructor function and return statement in j.s

mohandass — Tue, 07 Apr 2026 19:05:36 +0000

CONSTRUCTOR FUNCTION

A constructor function in JavaScript is a special function used as
blueprint to create and initialize multiple objects of the same type.
It defines the structure (properties) and behavior (methods) that every instance created from it will possess.
To create a object type we can use the constructor function.
It is considered to the good practice to name constructor function with an using a upper-case letter in the first letter
Create the constructor you must be called with the new operator

const car1={
brand: "ford",
price: 6,00,000,
color: "blue",

}

const car2{
brand: "tata",
price: 6,70,000,
color: "red",
}

It is the normal object creating method for car details
This type of method to using for two or three car details.If you can write the all ford car details so this method is too difficult
we can use the constructor function lets you reuse code to create many objects to easily with single line code

EXAMPLE:

EXPLANATION:

Create a function with write the parameters (brand,price,color)
Then use this to assign properties
Write a single line code for
const car1 = new Car ("ford",600000,"blue")

const car2 = new Car ("tata",670000,"red")

Use the new keyword,when use the "new" keyword for reason is you first create a function in "car" that is the new car
Then Print the full object like
console.log(car1)//Car{ brand: 'ford', price: 600000, color: 'blue' }
console.log(car2)//Car { brand: 'tata', price: 670000, color: 'red' }
If you want Print individual properties
console.log(car1.brand); // ford
console.log(car1.price); // 600000
console.log(car1.color); // blue

RETURN STATEMENT

The return statement in javascript is used inside a function to do Two main things.It stop the function from running and sends a values Back to whoever it called.
If the caller don't return a value.the value not used for any variable

EXAMPLE:

function add (a, b){
    return a + b;
}
 const result = add(5,20);
 console.log(result)

OUTPUT:
25

Creating a function named - add
It's take the two parameters a and b
return a + b; add the two values
Then sends back the result
If you call the function with values 5 and 20// a=5 , b=20 \it calculate 5 + 20=25
The return sends back "5"
The value is stored by variable "result"
Then print the result output is "25"

Objects in javascript

mohandass — Mon, 06 Apr 2026 17:28:38 +0000

In javascript an object is a standalone data structure used to Store collection of related data and more complex entities.Unlink Primitive data types like string or numbers.Store a single Value,object act as containers for multiple values organized as the Key-value pairs.
keys also called as properties (string or symbols)
Object are variables that store both values and function
Values can be anything : numbers,strings,arrays,function,or even Other objects
Object are one of the most important concept in javascript
Object is the mutable and dynamic properties it can be add,modify and delete at any time
Object contains methods and properties
Object are using with curly bracket {}

SYNTAX

const object name={
properties (key-pairs)
}

CRUD operation of object

C-(create)
R-(read)
U-(update)
D-(delete)

CREATE - Adding data

You can create a new object or new properties

Example:

name,age - are keys
mohan,25 - are their values

Output:
{ name: 'mohan', age: 25 }

READ - Access data

You can read a values using dot notation in the bracket notation

Example:

Output:
mohan
25

UPDATE - Modify data

You can change the existing values

Example:

Output:
mohan
27

Delete - Remove data

You can remove properties using the (delete) keyword

Example:

Output:
{ age: 27 }

REFERENCE:https://www.w3schools.com/js/js_objects.asp

Function in j.s

mohandass — Sun, 05 Apr 2026 05:10:23 +0000

Functions in javascript is the reusable blocks of code designed to Perform specific task.Instead of writing the same code again and Again you can put it inside a function and call it whenever needed.

SIMPLE IDEA

A function is like a machine,You can give a inputs it's called (parameters),it's processes and gives to back a output(called a return value).

SYNTAX

function ogadd(boys, girls);
return boys + girls;
}

Function is the keyword referring that we are writing a function
ogadd is the name given to the function it's used to call the function
boys and girla are the parameters inputs of the function it's like a Variable
return is the keyword if can used to the return the result once the Function is called
EXECUTION

let result = ogadd(25, 20);
console.log(result);

Once if you can calling the function is 25 and 20 are the arguments It's take the place of parameters boys and girls
It's runs the function addition operation returns the value 45 is Stored in the variable result
We have a returned the value it will stored in the variable result
SIMPLE UNDERSTANDING

Start with function is defined - ogadd
Next function is called - ogadd(25, 20)
Then assigned the value for boys and girls - boys = 25, girls = 20
Calculation - 25 + 20 = 45
The function returns 45
The return value 45 is stored in result
finely printing the result to the console.

Reference:https://www.w3schools.com/js/js_functions.asp

Array simple explanation with examples in j.s

mohandass — Thu, 02 Apr 2026 16:01:48 +0000

An array in javascript is a special type of variable that can store Multiple value in single place.

Instant of creating many variables

You can use the array

Ordered - Items have positions "if called indexes, starting from 0"
You Can store any type - numbers, strings, objects, and other arrays
Dynamic - You can add/remove elements anytime

If you can using (const)

You cannot reassign the array
But you can modify the content inside the array

const marks = [70,50,30,60,80]
0 1 2 3 4
Using a bracket starting mark value is "0",second mark value is "1",third mark value is "2",fourth mark value is "3" and fifth mark value is "4"

HOW TO FIND THE COUNT OF FAIL ?

If using a array and while loop method to find the fail count

const marks = [70,50,30,60,80]
let fail = 0;
let i = 0;
while (i < 5){
if (marks[i] < 35){
fail++;
}
i++;
}
console.log("fail count" ,fail)

Output:
fail count 1

STEPS :
step 1:Declare a mark in array using (const marks) in square brackets "[]" to order the values

step 2: we want how many fail count in the marks.we don't know how many fail count.So declare the name fail "let fail = 0"

step 3: Then declare the first elements of array is index. so start form 0 "let i = 0"

step 4: Next use the while loop (i < 5) because the array have a five Elements the index starting from 0 to 4

step 5: and then declare the if condition if(marks[i]<35)

step 6: if the condition is true increase the fail count "fail++"

step 7: increase the i inside the looping bracket
Important point : increase the i into the if condition that is "infinity loop"

step 8: And then print the fail count "console.log("fail count", fail)"

How working process in this program

we want the fail count above the mark.So declare the fail count is 0

2.Next declare the i = 0

3.if check the while loop condition
i=0
while (0 < 5)-condition is true

i=1
while(1 < 5)-condition is true

i=2
while(2 < 5)-condition is true

i=3
while(3 < 5)-condition is true

i=4
while(4 < 5)-condition is true

i=5
while(5 < 5)-condition is false so loop stop

Next check the if condition

index 0=70
if(marks[70]<35)-condition is false

index 1=50
if(marks[50]<35)-condition is false

index 2=30
if(marks[30]<35)-condition is true

index 3=60
if(marks[60]<35)-condition is false

index 4=80
if(marks[80]<35)-condition is false

4.If the condition is true fail count is increase.the index condition 0,1,3,4 it's all false.If the fail count not increase
The index 3 only true so the fail count is increase fail count is 1

5.Then finally when the loop is stop.Then print the fail count

OUTPUT: fail count 1

How to find count of fail and pass

And find a total marks

Flowchart for while looping

mohandass — Fri, 27 Mar 2026 09:08:06 +0000

what is looping in j.s

mohandass — Wed, 25 Mar 2026 15:50:31 +0000

looping in using javascript it's useful when you wand to a program The same task again and again without writing the same code Repeatedly
Different types of loops in javascript
- For loop
- While loop
- Do while loop
- For of loop
- For in loop

This are the looping types

Yesterday i learn start with ( while looping ). A while looping in Javascript is used to repeat of block a code in long as condition is True It is called an entry-controlled loop because the condition is checked before the code runs.

output:
0
1
2
3
4
(first start with i = 0)
(check condition i < 5)
(it's true run the code)
(increase i++)
(the repeat until condition becomes false)

Initialize - i = 0

Check condition - i < 5

Print - 0

Increment - i = 1

Check - i < 5

Print - 1

Increment - i = 2

Check - i < 5

Print - 2

Increment - i = 3

Check - i < 5

Print - 3

Increment - i = 4

Check - i < 5

Print - 4

Increment - i = 5

Check - i < 5 false Loop stops

Important point is if you don't update variable it running forever That is called (infinite loop)

How to clone a website

mohandass — Mon, 02 Mar 2026 18:07:05 +0000

Today i learn how to clone a website in visual studio code by using html .First I have to clone with a any kind of website i chose ILUGC-indian linux user's group chennai.I clone this website interface Before cloning website to draw a layout and i have using width,hight,margin to website layout and use
this is division tag this tag is used to divide header and body.
Adding logo and tittle with the header.For leaving a space inside a box is PADDING and outside a box is MARGIN,after setting margin border,width,height of a layout we move to header and set a navigation elements. In html there are two types of elements (inline elements),(block line elements).
After listing the elements flex elements direction into row.In html flex direction significantly denotes row direction for changing a row into column use FLEX DIERCTION-JUSTIFY CONTENT.To list a elements use ORDERED LIST and UNORDERED LIST.To align a columned elements into a row use CROSS AXIS-ALIGN ITEMS.

I'am learning full stack

mohandass — Sun, 01 Mar 2026 17:42:48 +0000

Yesterday i learned how to use dev.to in my class and discus that Dev.to using method.My sir teach the important and uses of dev.to it is the most valuable in interview and it is one of the helpful website and another useful application is linkedin
So many tech meeting on the linkedin and some group is free tech Meeting in tamil the group names are (code on JVM chennai and kanchi.lug) it is a complete open-source tech meeting and it's useful To learn
Also learn about how to install gitlab and use of the gitlab is to store html or css and any coding projects upload it's useful in our future interviews to show our projects in gitlab.Currently i'am using a 2.43.0 version it is very helpful application.