DEV Community: boopalan

July 8 blog

boopalan — Thu, 09 Jul 2026 14:43:51 +0000

As the continuation of the previous libre office impress i am create an animated matrix multiplication there is lot more needed to do in this, but i am happy to share that what i am done today

It seems like we are again going to restructure Tamilrulepy, really it holds a special place in my heart.

So, I am thinking Instead of abandoning of this workflow I am just planning to keep this code alive revisit it in the future,

Some would think giving up a closer one is a bit emotional, but I am eagerly waiting for the new workflow.

My learnings in python

decorator

A simple and easier way to define an instant decorator in python is easy.

If you see in some places developers will use three functions for defining decorator

One interesting thing i get is we can call decorator while using them in the top of the functions

@decorator
@decorator()

Calling a decorator in these two different ways helps to achieve several things.

july 7 blog

boopalan — Thu, 09 Jul 2026 14:24:35 +0000

i am create a ppt in libre office impress

I am forget to take a screenshot with VARUN

Myself I am, Varun meet in Tamilrulepy and just planned how to code most reliable way and most faster way,

Sathya Raj was deeply fascinated by the AI's coding capabilities. I was impressed by his prompt codes. It gives a way to think: is it possible to create a one workflow for getting rules through AI?

Suppose if you are using expo router tabs and if you are developing an app for two kinds of audiences. For example if you want to show a common ui for general users and different ui for the admin’s how can you do it?

I think this could cause a bit of trouble in achieving this one, but based on the database role it might be a simpler one, I need to work on this. If I complete this I will update here.

july - 5 blog

boopalan — Sun, 05 Jul 2026 14:42:48 +0000

Great time in the KanchLUG weekly meetup

ideas about some of the projects in the TOSSconf hackathon

idea about where we want to choose the sqlite and postgresql

The de Broglie Hypothesis,Matter Waves and Electron Diffraction,The Double-Slit Experiment
it remembers my schools day and physic class, here he taught in the Physics but It remembers my chemistry classes, my classes books this all are covered my chemistry classes.

I was the maintainer and developer of the tamilstring

I am planning to do at least two releases per year for an year so i am planned a release for this month.

need more contributions

Boopalan S / TamilString · GitLab

GitLab.com

gitlab.com

tamilstring-011d48.gitlab.io

july 4 blog

boopalan — Sun, 05 Jul 2026 11:50:03 +0000

One of my long day dream to make an app, I am a village there most of them depends the Arali flowers, literally I am and my family deeply connect this with this one flowers not only as our village and many more villages

how to get can I help them I can not do there work but I can help them to track there benefits

why we I am planning to build an app to track their daily revenue

It does not do any business but it helps to track their daily reviews.

for login it is for village and to the village peoples so initially I am planned to use the OPT login, But later I realised that it is more expensive service

I tried so alternatives like firebase, Whatsapp OTP, Amazon SNS, Twilio but in any way send messages in the highly expansive method of authentication

for development purpose firebase provides 10 free SMS daily so it just look to use this offer but I get errors only

finally it seems like working but I need to enable the GCP with the firebase blase plane from the spark plan so I am looking to do this in this week

and I am explore the supabase not I am saying most of the reviews say’s that supabase it the one of the best alternative for the firebase, just I am tried and create some table next thing is insert data, inserting one by one is a harder way so I am looking for an way to do it in cli, I not sure but it seems like they provide a cli

I am tried supabase expo using the email and password , at the first time if we register it will directly redirect the users to the home page but only in the first time

I will soon update if if any improvements in the app

TamilRulePy
after long time we meet again and we planed for what we need to next, we were planned to meet in the week days for building the app in the app, we just planned to meet in the coming Tuesday,

Array Iterations

boopalan — Wed, 24 Jun 2026 03:50:21 +0000

if we want to use the means we literlly do to the iterations manually

const fruits = ['banana', 'mango', 'jack','graph'];

console.log(fruits)
[ 'banana', 'mango', 'jack', 'graph' ]


for(let i = 0; i < fruits.length; i++){
    console.log(fruits[i]);
}

banana
mango
jack
graph

it looks easy if suppose if you i a complex position like this


const fruits = ['banana', 'mango', 'jack','graph'];

function callBackFunction( parameter ){
    console.log(value)
}

function callingEachElement( callBackFunction ){

    for(let i = 0; i < fruits.length; i++){
        callBackFunction(fruits[i]);
    }

}

callingEachElement( callBackFunction )

here we using an external function and calling the callback function
instead you writing the whole thing in a loop , how it would be easy if we do
in a one line, yes javascript have many functions do it, on those forEach is one of the
function, let we see forEach

forEach does not return any thing


fruits.forEach( (e)=> console.log(e) );
banana
mango
jack
graph

similary javascript have several functions, let we see them one by one

forEach does return anything but map will do the same thing and return
you an modify array


const fruits = ['banana', 'mango', 'jack','graph'];

function callBackFunction( value ){
    return value.toUpperCase();
}

function callingEachElement( callBackFunction ){
    const returning = [];
    for(let i = 0; i < fruits.length; i++){
        returning.push( callBackFunction(fruits[i]) );
    }
    return returning
}

result = callingEachElement( callBackFunction )

console.log(result)
[ 'BANANA', 'MANGO', 'JACK', 'GRAPH' ]



const ret = fruits.map( (e) => e.toUpperCase() );
console.log(ret);
[ 'BANANA', 'MANGO', 'JACK', 'GRAPH' ]

flatMap function


const intgers = [1,2,3,4,5,6,7,8,9,10];

function callBackFunction( value ){
    return [value, value*value];
}

function findSquare( callBackFunction ){
    const returning = [];
    for(let i = 0; i < intgers.length; i++){
        returning.push( callBackFunction(intgers[i]) );
    }
    return returning.flat();
}

result = findSquare( callBackFunction )

console.log(result)
[
   1,  1,  2,  4,  3,   9,  4,
  16,  5, 25,  6, 36,   7, 49,
   8, 64,  9, 81, 10, 100
]



const ret = intgers.flatMap( (e) => [e, e*e] );
console.log(ret);

[
   1,  1,  2,  4,  3,   9,  4,
  16,  5, 25,  6, 36,   7, 49,
   8, 64,  9, 81, 10, 100
]

filter function


const intgers = [10,5,7,3,2,8,4,1,6,9];

function callBackFunction( value ){
    if (value <= 5){
        return value
    }
    else{
        return false
    }
}

function findSquare( callBackFunction ){
    const returning = [];
    for(let i = 0; i < intgers.length; i++){
        res = callBackFunction(intgers[i]);
        if (res != false){
            returning.push( res );
        }
    }
    return returning
}

result = findSquare( callBackFunction )

console.log(result)


const ret = intgers.filter( (value) => {
    if (value <= 5){
        return value
    }
} );
console.log(ret);

reduce function


const intgers = [10,5,7,3,2,8,4,1,6,9];

function callBackFunction( total, value ){
    console.log(total, value)
    return total + value
}

function findSum( callBackFunction ){
    let returning = 0;
    for(let i = 0; i < intgers.length; i++){
        res = callBackFunction(returning,intgers[i]);
        returning += res
    }
    return returning
}

result = findSum( callBackFunction )

console.log(result)


const ret = intgers.reduce( (total , values) => total);
console.log(ret);

Arrays length, pop and at functions

boopalan — Tue, 23 Jun 2026 15:40:26 +0000

Suppose if you want to get the length of an array, how we will get it,
we usually do looping and get the count of the length

const fruits = ['banana', 'mango', 'jack','graph']
count = 1
for (const f of fruits){
    count += 1
}

console.log(count)

but length will doing all the whole just in one line

const fruits = [banana', 'mango', 'jack','graph']
console.log(fruits.lenght)

In array at method helps to indexing and also it supports negative indexing

By default when we use the square brackets to get the arrays elements it does not
support the negative indexing but at method helps for the negative indexing also,

in programming logic some scenarios negative indexing helps in many places

example

indexing


const fruits = ['banana', 'mango', 'jack','graph']
console.log(fruits[2]) //jack
console.log(fruits.at(2)) //jack

negative indexing

const fruits = ['banana', 'mango', 'jack','graph']
console.log(fruits[-2]) //jack
console.log(fruits.at(-2)) //jack

if you use the out of the index in any of thus method both methods it always get the
undefined

const fruits = ['banana', 'mango', 'jack','graph']
console.log(fruits[8]) // undefined
console.log(fruits.at(8)) // undefined

const fruits = ['banana', 'mango', 'jack','graph']
console.log(fruits[-8]) //  undefined
console.log(fruits.at(-8)) // undefined

join function

this function helps to join the each elements to gather and return a string


const fruits = ['banana', 'mango', 'jack','graph'];
const joinedFruits = fruits.join(" ");
console.log(joinedFruits) 
// 'banana mango jack graph'

const joinedFruits = fruits.join("*");
console.log(joinedFruits) 
// 'banana*mango*jack*graph'

objects in JavaScript part-2

boopalan — Fri, 19 Jun 2026 11:03:25 +0000

javascript part-1

how we do not use the keys
if you keys have more the own words then you can add the double quotes around it

example:

const obj3 = {
    “is admin” : false,
    // here the key have two words so we are using the double quotes
}
//obj3.is admin

// If you try to access like this way javascript consider it self obj3 having a is property and leave it the remaining

In this case we can use like this way, now it will retrieve the values of the properly

console.log(obj3[“is admin”]);
//false

can can also add some of the properties in this similar ways
examples

obj3[“is user”] = true;
console.log(obj3[“is user”]); // true

same as it allows us to modify values in the properties

obj3[“is admin”] = true;
console.log(obj3[“is admin”]); // true

now it was changed from the false to true values

how to remove any of the keys in the object, whenever we remove any of the keys its respective values will also remove from the objects

delete obj3[“is admin”] = true;
console.log(obj3)

you cannot see the “is admin” key in this object because the delete key word helps us to remove keys.

some of the way to handle the objects dynamically

let we consider we have this kind of object

const user = {
    name : “boopalan”
}
const role = “Java fullstack developer”;

if we try to add the role as key to user object how we will do it

user.role = role
user[“role”] = role

however we can add the role key to the the user object in any way, the we will usually access the role key in this this way

console.log( user[“role”] );
console.log( user.role );

Here actually we took two steps to add and access the key and values, how it would be easy if we do it in a single line or one step, ya JavaScript provides a dynamic way to add and access the key in one single step.

Console.log(user[role]);

here the role is dynamically added in the object and then it in this usual way we are accessing the behaviours

if we want to use this dynamic method we must have to declare the variables before use it.
Here we actually predefined what is the key want to be in the object

how can we set the key names dynamically is it possible we can be able to use the key dynamically without hard coded
Yes, we are able to do it let us see how to do it?

Const key = prompt(“ what key you want to add : ”)
cost dynamicObject = {
    [key] : “values for the key”,
    // here whatever give to the key that will automatically converted into the key
}

console.log(dynamicObject )

constructor function
we know about how to create and use the functions in javascript, we can use the functions to create object

function LLM(name, parameters){
    this.name = name,
    this.parameters = parameters
}

if we plan to use the constructor function to create object we must need ti use the new keyword


function Person(name, age) {
this.name = name;
this.age = age;
}
// Creating a new object using the constructor function
const johnDoe = new Person('John Doe', 30);
if we create without new keyword
const Gorge = Person(‘Gorge’, 30);
console.log(Gorge) //undefined

what will happen if we do not use the new keyword

strict mode TBD

non-strict mode, this points to the global window object. In strict mode, this is undefined
this will lead to polluted window object
to ensure what was happening without the new keyword let we see

console.log(window.name) // Gorge
console.log(window.age) // 30

do you notice that this time if we use the constructor function to create objects it will say out object was function type, up to no or if we use the object literals it would not say any types for the object, this is where constructor function helps to create use defined function instead of default object types

to check the instances

console.log( johnDoe instanceof Person ); //
this will helps to check the which object we are handling

Also javascript provides it’s one object type, so we do not need to create an extra function manually to create objects

const person = new Object();
person.name = “matz”
console.log(person)

this does not show any new types for this object

using function in the objects

const profile = {
    name : “matz”,
    getName: function () {
        console.log(` username is ${this.name}`)
    }
}
console.log(profile.getName())
// you must use the braces to call the function

how to handle the not existing properties in the object
If we try to call the not existing properties javascript will say does not undefined

console.log(person.salary) // undefined

one way to check is in operator
console.log(‘salary’ in person) // false
because the salary property is not in the person object

console.log(person.hasOwnProperty('age')); true

this hasOwnProperty() will say that an object does it has an property or not by passing the an argument to this function

If you are a situation of out want handle the nested objects in will help very much


const profile = {
    name : “matz”,
    countries : {
        asia : [“Japan”, “China”]
        europe : [“German”, “France”]
    }
}
for (let key in profile) {
    console.log( key )
    // this time we get all the keys from the person object
    console.log( profile[key} )
    // similarly key help to get the values
}

how to get all the keys form an particular objects
Objects.keys(person)

this will return all the keys in a array data type

NOTE
objects is always stored in and shared by the references

object references


const favFruit = { name = “mango” };
const seasonalFruit = {name = “mango”};

console.log( favFruit == seasonalFruit ); // false
console.log( favFruit === seasonalFruit ); // false

whether comparison operators (==) and strict equality operator (===) both will give a false result because it will check only the references of the both objects, not the item by item inside.

const seasonalFruit = {name = “mango”};
let favFruit = seasonalFruit
console.log( favFruit == seasonalFruit ); // true
console.log( favFruit === seasonalFruit ); // true

this time we get false because both variables have the same references, so the both comparison operators (==) and strict equality operator (===) check it’s references and return true because both have the same references

static methods

const target = { p:1, q:2};
const source = { a:3 , b:5};
const returnObject = Object.assign(target, source);
consle.log( returnObject);
here we will get an object that having the both objects properties, here in the above example we do not have repeated properties so it compliments both objects properties and return them

suppose any one them have an repeated property then what will happen
let we see them
const target = { p:1, a:2};
const source = { a:3 , b:5};
const returnObject = Object.assign(target, source);
consle.log( returnObject);
here the repeated property was overwritten by the last value having the same property names

const target = { p:1, a:2};
const returnObject = Object.assign({}, source);
consle.log( returnObject);

here the second objects the source was copied and we get its properties at the final output

NOTE we was getting the new references each time not the same references of the copied objects
to verify that it was an object new references

console.log( returnObject == target ); // false
console.log( returnObject === target ); // false

shallow copy vs deep copy

let we check does the assign object

const source = { a:3 , b:5, c:{ x:0}};
const returnObject = Object.assign({}, source);

first we check that is both object have the same properties after cloning

console.log( source );
// { a:3 , b:5, c:{ x:0}}
console.log( returnObject);
// { a:3 , b:5, c:{ x:0}};

it seems like both have the same number of objects
what will happen if we change the values of the properties

returnObject.a = “100”;
consle.log( source.a ); // 3
consle.log( returnObject.a ); 100

it copies the primary key of the objects
let we try to change the values of the child objects

returnObject.c.x = “100”;
consle.log( source.c.x ); // 100
consle.log( returnObject.c.x ); 100

here if we change the values of the child objects it properties it affects the both simultaneously

What are objects in JavaScript?

boopalan — Thu, 18 Jun 2026 03:01:14 +0000

What are objects in JavaScript?
Suppose if you are in a situation of using same and repeated variables again and again, to reduce this kind of again and again declaration of same kind of variable objects will reduce this problem in programming, it a kind of key and value pairs, it does not allow repeated duplicated keys and you can store primitive and not primitive data types as values to the objects keys.

How to create objects

JavaScript allows us to create objects in several ways, for example object literals, object constructors and many more ways.

Creating object using the object literals

const obj1 = {
    name:”yukihiro matsumoto”,
    language: “Japanese”
}

here each key should be separated by the commas, it allows to identify each key and values respectively.

To access the values in the object we have to use the object variable along with dot and the you can specify which key why want to call

console.log(“obj1.name”)
//  yukihiro matsumoto

console.log(“obj1.language ”)
//  Japanese

Why are we using const for objects?

Why do you notice that we are using const for the object variables, then you may ask why you are using const? By using const, are we able to change the values of any of them?

Let us see one by them, why const?
Const will key the object reference same and we are only changing the values inside the same references, but if we use any other variable keyword it will allow to change the variable’s references
In any way we are able to modify and object key values.

Creating objects form existing variables

let say you already have some of the variables

const a = “Apple”;
const b = “Ball”;
const c  = “cat”;

if you want to use this variable’s values in your new object you can use its values

const abc = {
    a : a,
    b:b,
    c:c
}

instead also we can able to use the short hand notation for creating objects using this variable in for the object creation

const abc = {
    a , b, c
};

let we see how to change the values of the keys

const obj1 = {
    name:”yukihiro matsumoto”,
    language: “Japanese”
}

obj1.name = “Brendan Eich”;
obj1.language = “English”;

console.log(obj1)

// { name : “Brendan Eich” , language : “English” }

let we see the how to create the Object using the object constructor

const obj2 = new Object();

obj2.name = “Rasmus Lerdorf”;
obj2.language = “English”;

// { name : “Rasmus Lerdorf” , language : “English” }

Why we need TypeScript rather then JavaScript?

boopalan — Mon, 15 Jun 2026 15:41:26 +0000

What is typescript?
We can say it is simply superset of the javascript that means we can write all the javascript code inside the typescript. Why will this question rise, then why should we use Typescript instead of Javascript. Basically some of the additional features were supported or provided by the Typescript that are not available in the Javascript.

They are Strong Typing, Object Oriented Features, Compile Time Errors 

Typescript was finally converted into Javascript because not all the browsers have the same version of JavaScript. So companies need to support all the browsers not all users use the save Browsers and as well as same platform. To resolve these kinds of issues the Typescript compiler compiles the Typescript code to common code that will run in all the browsers.

How to install typescript

first we need the JavaScript runtime environment in our platform

to check the installation

node -v

to check the node package manager

npm -v

to install typescript in our computer we have to install the typescript package using the node

npm install -g typescript

download and install the typescript globally in our system. So in this way we can typescript anywhere in our computer using the tsc command

tsc -v

// file.js
var teststring  = “this is a string”;
teststring = 1;
teststring = function (a , b) {return a+b};
console.log(teststring );

This javascript code says that we are unable to use any fixed value for this teststring variable. For this small code this is ok but if I face this kind of problem in the production means literally it can take a long debugging time. So to avoid those kinds of issues we can use the typescript, it will say all the errors in the compile time, it helps to resolve immediately before the production it reduces the debugging time.

To avoid all these conflicts, if we define type for each variable what it should want to be, by this way we do not need to worry about getting any other types. Typescript ensure what type want to be in each variable.

file.ts
var teststring: string  = “this is a string”;
teststring = 1;
// now it would not all to define any other type rather than the string
teststring = function (a , b) {return a+b};
// same as now it would not all to initialise the function for this variable
console.log(teststring );

let we try to compile this typescript code

tsc file.ts

we can able to see the compile this Typescript code compiler error but it would not stop the compilation, it ensures the same types

how many types in the JavaScript

var mystr:string = “test”;
var mynum: number = 100;
var mybool : boolean  =true; 

mystr = 100;
mynum = true;
mybool = “true”;

If we use a typescript extension installed with texteditor, we can be able to see the error in the editor to resolve them.

Even if we compiled it, the type script compiler will show the errors however the code will be compiled into javascript.
We can test it in the node or any other javascript runtime environments.

conditional operator

boopalan — Thu, 04 Jun 2026 16:59:48 +0000

Assignment operators in javascript
assignment operator is used to assign values to the variables, if we assign a different value for again and again the operator will assign the values what we finally assign to it.
Example

> a = 10
10
> a = "hello"
'hello'
> a = []
[]
> a = {}
{}

combination of assignment operator with the arithmetic operations

addition assignment operator ( += )
subtraction assignment operator ( -= )
multiplication assignment operator ( *= )
division assignment operator ( /= )

Comparison Operators
it checks the left and right hand sides values is whether it is equal or it is not equal, wherever want to compare two values in our programs logic. Based on the scenario we not only need use the equality some time we may need not equal less the, greater than and so on, let we see one by one some of the javascript comparison operations

loose equality ( == )
strict equality ( === )
loose inequality ( != )
strict inequality ( !== )
greater than ( > )
less than ( < )
greater than or equal ( >= )
less than or equal ( <= )

Logical Operators

it is used to determine the logical flow of program, we may need some time our program want to follow more than one condition on those scenarios we have to check all the condition in this case we can use AND logical operator, some time we have to any one of the condition, other then this we can do NOT operator it will help to check was it is opposite to our specified term.

AND operator ( && )
OR operator ( || )
NOT operator ( ! )

conditional operator

In our program flow whenever we want to do some specific tasks we can do those things in the conditional operator. If we want to run a block of code for specific conditions we can be able to do it, in addition we can add as many conditions as possible.

It looks block by block, we can specify if we want to check all the conditions, any one of the conditions. Whenever the conditions pass it executes the block of code.

Examples

here we are going to check does out values is passes or if not passes

zero = 0;
if ( zero == 0) {
    console.log(“here our condition is passes”)
}

here our condition is passes, hence because of our condition passes so it run the block inside the if block

example for opposite case if our condition was not pass


zero = 1;
if ( zero == 0) {
    console.log(“here our condition is passes”)
}

using else block

instead of skipping if our if condition fails, suppose if we want to execute any other block whenever our if condition fails in those cases we can use the else block

odd = 1;
even = 2;
if (odd == even){
console.log("they equal")
}
else{
console.log("not equal")
}

NOTE: we cannot use directly without else condition block without if condition block.

we cannot use it directly
else{
console.log("not equal")
}
``



Else if block



    up to now we only seen if and else block, if we want to check one then one conditions we can use many if’s along with the else so that instead of skipping that block it check condition and if passes the block will executes

marks = 100

if (mark >= 90){
console.log(“Grade A”)
} else if(mark >= 80){
console.log(“Grade B”)
} else if (mark >= 60){
console.log(“Grade C”)
} else {
console.log(“Grade D”)
}

RCB = 20
CSK = 23

if (RCB > CSK) {
console.log(“RCB wins”)
}
else if(CSK > RCB){
console.log(“RCB wins”)
}
else{
console.log(“DRAW”)
}

marks = 80
attendance = 4

if ( mark => 60 && attendance >= 2 ){
console.log(“PASS”);
}
else{
console.log(“FAIL”);
}

implicit and explicit type conversion and Arithmetic operations.

boopalan — Wed, 03 Jun 2026 15:27:19 +0000

implicit type conversion

for doing operation in between the type need same types. But in real world programming we cannot always expect that we will be performed in between the same types. In those cases we have to handle different types, JavaScript has some in-built behaviours to handle different types, that is called implicit type conversion.

It will automatically convert the other type to a suitable type for doing operation whenever needed.

For example if we do an addition operation in between the string and the number.

“hi” + 4

it was converted that another type to string

is it similar if we do

“hi” + 4

in another case suppose if we do subtraction in between the two type what will happen

“10” - 30

this time we will get different answer because instead of converting one type to another type it convert the string into to Number type(we cannot be perform subtraction between the string types, so it convert the string to Number and we finally get the -20)

explicit type conversion:

What is the difference between Implicit and Explicit Type Conversion?

implicit: Done automatically by the compiler. It safely promotes smaller types to larger types (e.g., short to int or int to double) to avoid data loss.

Explicit (Casting): Manually enforced by the developer using a cast operator (e.g., (int)myDouble). It is used to convert larger types to smaller types, carrying a risk of truncation or data loss. [1, 2, 3, 4, 5]

TBD

what will happen If we need to convert the Non-Premitive types to non primitive type case
can we be able to do operations between the non-primitive types.

subtraction operator

just like the name it is used to perform the operation between the Number types of element

examples (trying this in the browsers console or any other JavaScript runtime environments in the machine )

10 -5 // 5
50-50 //0

**
multiplication operator**

if we perform operation between the Number it will multiplay, But if we perform the operation between the String and the number it will return NaN(not a number)

10 * 10 // 100
“10” * 10 // NaN

division operator
As well as division is one fundamental operation in the maths and it will helps for us in several area

10/1 // 10
5/5 // 1

In this example it gives us Number type, suppose if we perform an operation that gives us irrational numbers, then how it will be handled by the JavaScript.

Example

it is runned inside the nodejs

> a = 10
10
> b = 7
7
> c = 10/7
1.4285714285714286
> typeof(c)
'number'
>

when you notice the type of the c, it value is irrational but if we see the type it is actually a number,

In many other programming languages the float or irrational number is considered as the different data type but in JavaScript it is considered as the Number.

modules operator
to check the remainder between two number will help many scenarios, For example to find the odd or even


> 11%2
1
> 11%3
2
> 11%11
0
> 11%1
0
> 23%3
2

exponential operator
it is used to find the square of a math number.

> 2**3
8
> 2**1
2
> 2**0
1
> 5**10
9765625
>2**3
8

increment operator
most case we will use the increment operation in the for loop and while loop, here we will see that how it was working

let I = 1;
I = I + 1
console.log(I) // 2

let I = 1;
I ++
console.log(I) // 2

decrement operator
Just like the increment we will use the decrement operator, it also works like the increment but instead of increasing count it reduces the count.

let I = 1;
I = I - 1
console.log(I) // 0

let I = 1;
I --
console.log(I) // 0

post increment and decrement operator

It see the increase operation deeply it was actually first use the values in stored in the variable and later it is increase the value that’s why it is called post increment

post increment operator


let I = 1;
console.log(I++) // 1
console.loglet


I = 1;
I ++;
console.log(I++) // 2(I) // 2

post decrement operator

let I = 1;
console.log(I--) // 1
console.log(I) // 2


let I = 1;
I --;
console.log(I--) // 2

**
pre increment and pre decrement operator**

suppose if do now want to use the values first and then increase the value in the variable, you want to first increment or decrement the value first and then you want to use the values in the program you also do that with the help of the pre increment and pre decrement operators

pre increment operator

let I = 1;
console.log(++I) // 1
console.log(I) //

I = 1;
++I;
console.log(I++) // 2(I) // 2

pre decrement operator

let I = 1;
console.log(--I) // 1
console.log(I) // 2


let I = 1;
--I;
console.log(I) // 2

Question of the question based on our learnings

let I =5;
let j = 7;
result = i++ - --j + ++j i++;
log(i,j,result)

Variable in javascript

boopalan — Wed, 03 Jun 2026 03:42:42 +0000

javascript is a dynamically typed programming language, so we do not need to use the type while using the variable values.

Variable declaration?

First we want to define the variable name, only defining a variable is a declaration. Later you can give the values to those variables

example

variableDecleration;

*declaration and initialisation *

suppose if you define and give the values in the same line then it is said as both the declaration and initialization.

example

username = “ajith”;

Later we can use this variable wherever we want to use the values in the variable.

Keywords in variable declaration.

Simply we can declare a variable without any keyword like the above one. But it is not a preferred way to create variables in javascript. There are some preferred ways to declare variables in javascript. Let We see them one by one

*using var keyword *

It is the initial keyword used in javascript to define variables. To define variables but it caused many issues in the later part of the code. Let we see them how it case problem in later part of the code
it allows the variables to be defined several times, it reduces the code quality of the code.

Example

    var zero = 0;
    //  code 
    // if use define the code once again it again create the variable again 
    // defining the same variable again and again is not good code, it reduces the code quality.
    var zero = “hello”

to reduce the issues and drawbacks in the var keyword they created the let keyword.

Let stops the develops to define the variable again

Example

let zero = 0;
    //  code 
    // if use define the code once again it again create the variable again 
    // defining the same variable again and again is not good code, it reduces the code quality.
    let zero = “hello”
    // this time javascript would not allow the developers to define once again 

but it allows the developers to change the values of the variable

example
    let username = “user1”
    username = “adminuser” // it allows to change the values

Sometimes we do not need to change the values again. For those cases they introduce another keyword.

Const keyword
it does not allow the developers to again and again, also it does not allows to change the values of the variables those using the const keyword

example

const isAdmin = true;
    const isAdmin = false; // it does not allow to change the values again
    isAdmin = 0; it does not allow the define again ;

arithmetic operation in javascript

addition

10 + 4 = 14
30 + 10 = 40

exmple

let a = 20;
let b = 30;
let c = a + b;
console.log(c) // 50

in other types of datas

“10” + 1 = 101

subtraction

15 -5 => 10
5 -15 => -10

let a = 20;
let b = 30;
let c = a - b;
console.log(c) // -10

suppose if we have other then number casues this kind of issues
‘15’ -5
10 + “5”
10 + true

here it will try to convert the types two different types into same time, for that it will convert the sting to number, here we are given the number as a sting and we got the result

suppose if we define the a string as a number what will happen
‘abc’ -5

it will try to convert the non numbers to number, here the ‘abc’ are not number so it say ‘NaN’

and NaN + number is NaN