DEV Community: JEGADESHWARAN B

objects in JavaScript

JEGADESHWARAN B — Fri, 10 Apr 2026 14:41:13 +0000

🧠 Objects in JavaScript — A Simple and Complete Guide

After understanding functions as workers, the next important concept is objects.

If functions are workers, then:

Objects are like real-world things that store data and behavior together.

🌱 What is an Object? (First Principle)

An object is like a person or thing that has:

properties (data)
actions (functions)

🧒 Real-Life Analogy

Think of a tea shop owner:

Name → Arun
Age → 25
Job → Making tea

And he can:

make tea
take orders

👉 That is exactly what an object is.

⚙️ Basic Definition

An object is a collection of key-value pairs, where values can be data or functions.

☕ Simple Example

```javascript id="k0f8kp"
const teaShop = {
owner: "Arun",
location: "Erode",
makeTea: function() {
console.log("Tea is ready");
}
};




---

👉 Here:

* `owner`, `location` → properties
* `makeTea` → function (method)

---

# 📦 Accessing Object Data



```javascript id="3zv2n5"
console.log(teaShop.owner);       // Arun
teaShop.makeTea();                // Tea is ready

🧠 Objects + Functions (Important Connection)

When a function is inside an object, it is called a method.

```javascript id="k2p4zj"
const user = {
name: "Jegan",
greet() {
console.log("Hello " + this.name);
}
};




---

👉 `this.name` refers to the object itself.

---

# 🎭 The `this` Keyword

> `this` means “the current object”



```javascript id="9f4gq2"
const person = {
    name: "Arun",
    speak() {
        console.log(this.name);
    }
};

✔ this = person object

🧾 Creating Objects (Different Ways)

1. Object Literal (Most Common)

```javascript id="3xvmbu"
const car = {
brand: "Toyota",
start() {
console.log("Car started");
}
};




---

## 2. Constructor Function



```javascript id="0m9z1p"
function Car(brand) {
    this.brand = brand;
}

const c1 = new Car("Honda");

3. Using `class` (Modern Way)

```javascript id="p5yd4o"
class Car {
constructor(brand) {
this.brand = brand;
}
}




---

# 🔁 Objects are Dynamic

You can add or change properties anytime.



```javascript id="0z9xxf"
const user = {};

user.name = "Jegan";
user.age = 22;

🧠 Objects are Reference Types

```javascript id="mbg1tx"
const a = { name: "A" };
const b = a;

b.name = "B";

console.log(a.name); // B




👉 Both point to the same object in memory.

---

# 🧪 Useful Object Methods

---

## Object.keys()



```javascript id="y4whbq"
Object.keys(teaShop);

Object.values()

```javascript id="y5o0o1"
Object.values(teaShop);




---

## Object.entries()



```javascript id="8tvjv2"
Object.entries(teaShop);

🌍 Real-World Example

User Object (CRM App)

```javascript id="mtu3kk"
const user = {
id: 1,
name: "Jegan",
email: "jegan@gmail.com",
login() {
console.log("User logged in");
}
};




---

## Transaction Object



```javascript id="4k2b7x"
const transaction = {
    amount: 5000,
    type: "expense",
    category: "rent"
};

🔗 Objects + Functions Together

Objects store data
Functions operate on data

Together, they build applications.

🧠 Final Understanding

An object is a real-world entity in your program that groups related data and behavior together.

🧒 Simple Definition (Child Level)

An object is like a person or thing that has information and can do actions.

🚀 Conclusion

Objects help you:

Organize data
Represent real-world things
Build structured applications

👉 In short:

Objects are containers of data and behavior in JavaScript.

If functions are workers,
then objects are people or things those workers belong to.

Function in JavaScript

JEGADESHWARAN B — Fri, 10 Apr 2026 04:24:35 +0000

🌱 What is a Function? (First Principle)

A function is like a worker.

Just like a tea master in a shop:

You give an order
The tea master prepares tea
The tea is given back to you

👉 In programming:

A function is a reusable block of code that takes input, performs a task, and optionally returns output.

☕ Simple Example

function makeTea() {
    console.log("Tea is ready");
}

makeTea();

👉 Here:

makeTea = worker
calling it = giving instruction

📥 Functions with Input (Parameters)

Workers become more useful when they accept instructions.

function makeTea(sugar) {
    console.log("Tea with " + sugar + " spoons of sugar");
}

makeTea(2);
makeTea(1);

👉 Same function, different results.

📤 Functions with Output (Return Value)

Some workers not only do work — they give results back.

function add(a, b) {
    return a + b;
}

let result = add(5, 3);

👉 return sends the result back.

🧾 Types of Functions

1. Function Declaration

function greet() {
    console.log("Hello");
}

✔ Can be used before it is written (hoisting)

2. Function Expression

const greet = function() {
    console.log("Hello");
};

❌ Cannot be used before definition

3. Arrow Function

const add = (a, b) => a + b;

✔ Short and modern syntax

🧠 Functions are First-Class Citizens

In JavaScript:

Functions are treated like values.

That means:

They can be stored in variables
Passed as arguments
Returned from other functions

Example:

function sayHello() {
    return "Hello";
}

function execute(fn) {
    console.log(fn());
}

execute(sayHello);

🔁 Callback Functions

A callback is a function passed into another function.

function processTask(callback) {
    console.log("Processing...");
    callback();
}

processTask(() => {
    console.log("Done!");
});

⏳ Asynchronous Functions

JavaScript can run tasks later without stopping everything.

setTimeout(() => {
    console.log("Task completed");
}, 2000);

🚀 Promises

Promises make async code cleaner.

const promise = new Promise((resolve) => {
    resolve("Success");
});

promise.then(result => console.log(result));

✨ Async/Await

Modern and easy way to handle async operations.

async function getData() {
    let response = await fetch("url");
    let data = await response.json();
    return data;
}

🔐 Closures

A closure allows a function to remember its outer variables.

function counter() {
    let count = 0;

    return function() {
        count++;
        return count;
    };
}

const c = counter();

c(); // 1
c(); // 2

🧭 Scope

Scope defines where variables can be accessed.

function outer() {
    let x = 10;

    function inner() {
        console.log(x);
    }

    inner();
}

🎭 The `this` Keyword

this refers to the object calling the function.

const user = {
    name: "Jegan",
    greet() {
        console.log(this.name);
    }
};

🏗️ Constructor Functions

Functions can create objects.

function User(name) {
    this.name = name;
}

const u1 = new User("Jegan");

🧪 Higher-Order Functions

Functions that use other functions.

const numbers = [1, 2, 3];

const doubled = numbers.map(n => n * 2);

⚙️ Behind the Scenes

When a function runs:

JavaScript creates an execution context
Uses a call stack to manage execution

🌍 Real-World Usage

Functions are used everywhere:

Backend (APIs, controllers)
Frontend (events, UI updates)
Data processing
Business logic

🧠 Final Understanding

A function is a reusable worker in your program.

It can:

Take input
Perform a task
Return output
Work with other functions
Manage data and logic

🧒 Simple Definition (Child Level)

A function is a helper that does a job when you ask it.

🚀 Conclusion

Functions are not just a feature of JavaScript —
they are the foundation of everything you build.

If you master functions, you master JavaScript.

Login Access Check

JEGADESHWARAN B — Fri, 03 Apr 2026 15:52:50 +0000

you have:
username
password
isBlocked(boolean)
allow login only if:
username is "admin"
password is "1234"
user is not blocked
otherwise print appropriate message.

let username= "admin";
let password = "1234";
let isblocked = true;

if(username==="admin" && password==="1234"){
if(isblocked){
console.log("user is blocked");
else{
console.log("logged in");
}
else{
console.log("username or password incorrect");
}

Shopping Discount System

JEGADESHWARAN B — Fri, 03 Apr 2026 15:47:19 +0000

You have:
amount
isMember(boolean)

A user buys products worth amount.
if amount ≥ 5000 => 20% discount
if amount ≥ 2000 => 10% discount
therwise => no discount
members get extra 10% discount
Print final price after discount.

let amount=1000;
let isMember = false;
const MemberDiscount = 10;
let discount = 0;
if(amount>=5000){
 discount = 20;
  }
  elseif(amount>=2000){
  discount = 10;
  }
  else{
  if(isMember){
  console.log(amount - (amount*(discount+MemberDiscount)/100));
  }
  else{
  console.log(amount - ((amount*discount)/100));
  }
  }

Operators in JavaScript

JEGADESHWARAN B — Mon, 30 Mar 2026 08:33:54 +0000

What are Operators in JavaScript?

Operators are symbols used to perform operations on values (called operands).
Example:

let result = 10 + 5;

Here:

10 and 5 → operands
+ → operator

Types of Operators (Basic Idea)

Some common operators:

Arithmetic → +, -, *, /
Assignment → =, +=
Comparison → ==, ===
Logical → &&, ||

Now we focus on Arithmetic operators (+ and -)

Addition (+) Operator

How it works:

If both values are numbers → addition
If any one is string → convert to string
Then join (concatenate)

Examples

Number + Number

javascript
console.log(10 + 5); // 15

String + String

console.log("Hello" + " JS"); // "Hello JS"

String + Number

console.log("10" + 5); // "105"

Number + String

console.log(10 + "5"); // "105"

Subtraction (-) Operator

How it works:

Convert both values to numbers
Perform subtraction
If not possible → NaN

Examples

Number - Number

console.log(10 - 5); // 5

⚠️ String - Number

console.log("10" - 5); // 5

Number - String

console.log(10 - "5"); // 5

String - String

console.log("10" - "5"); // 5

Invalid String

console.log("Hello" - 5); // NaN

Final Difference

Operator	Behavior
`+`	Can add OR join strings
`-`	Always numeric subtraction

Easy Memory Trick

console.log("5" + 5); // "55"
console.log("5" - 5); // 0

+ → string joins
- → number math only

Polymorphism in java

JEGADESHWARAN B — Mon, 16 Feb 2026 06:59:23 +0000

Initial

Polymorphism means many forms.
It allows methods to perform different tasks.

Depth

It increases flexibility in programs.
It allows method overloading and method overriding.

More Depth

Compile-time polymorphism uses overloading.
Run-time polymorphism uses overriding.

Final

Polymorphism allows one interface to have multiple implementations.

Inheritance in java

JEGADESHWARAN B — Mon, 16 Feb 2026 06:58:22 +0000

Initial

Inheritance is a feature of OOPS.
It allows one class to acquire properties of another class.

Depth

It promotes code reusability.
It creates a parent-child relationship between classes.

More Depth

Types include single, multiple, multilevel, hierarchical inheritance.

Final

Inheritance enables reuse of existing class features in new classes.

this keyword in java

JEGADESHWARAN B — Mon, 16 Feb 2026 06:56:58 +0000

Initial

The this keyword refers to the current object.
It is used inside class methods.

Depth

It differentiates instance variables from local variables.
It can call current class methods and constructors.

More Depth

Commonly used when variable names are the same as parameters.

Final

The this keyword represents the current class object

OOPS (Object oriented Programming System)

JEGADESHWARAN B — Mon, 16 Feb 2026 06:55:59 +0000

Initial

OOPS is a programming approach.
It is based on objects and classes.
It organizes code in a structured way.

Depth

It focuses on real-world entities.
It improves code reusability and security.

More Depth

Main concepts include class, object, inheritance, polymorphism, encapsulation, abstraction.

Final

OOPS makes programs modular, reusable, and easy to maintain.

Continue statement

JEGADESHWARAN B — Mon, 16 Feb 2026 06:51:08 +0000

Initial

The continue statement skips current iteration.
It moves to the next loop cycle.

Depth

It does not terminate the loop.
It only skips remaining code in that iteration.

More Depth
Used to avoid specific conditions inside loops.

Final

The continue statement skips to the next iteration of a loop

Break statement

JEGADESHWARAN B — Mon, 16 Feb 2026 06:49:46 +0000

Initial

The break statement stops execution.
It exits from loop or switch.

Depth

Control moves to the next statement after the loop.
It prevents unnecessary execution.

More Depth

Commonly used in switch and loops.

Final

The break statement terminates the current block.

Jumping statement

JEGADESHWARAN B — Mon, 16 Feb 2026 06:48:46 +0000

Initial

Jumping statements alter normal flow.
They transfer control immediately.

Depth

They are used inside loops or switch.
They interrupt normal sequence.

More Depth

Examples include break and continue.

Final

Jumping statements change program execution flow instantly.

DEV Community: JEGADESHWARAN B

objects in JavaScript

🧠 Objects in JavaScript — A Simple and Complete Guide

🌱 What is an Object? (First Principle)

🧒 Real-Life Analogy

⚙️ Basic Definition

☕ Simple Example

🧠 Objects + Functions (Important Connection)

🧾 Creating Objects (Different Ways)

1. Object Literal (Most Common)

3. Using class (Modern Way)

🧠 Objects are Reference Types

Object.values()

🌍 Real-World Example

User Object (CRM App)

🔗 Objects + Functions Together

🧠 Final Understanding

🧒 Simple Definition (Child Level)

🚀 Conclusion

Function in JavaScript

🌱 What is a Function? (First Principle)

👉 In programming:

☕ Simple Example

📥 Functions with Input (Parameters)

📤 Functions with Output (Return Value)

🧾 Types of Functions

1. Function Declaration

2. Function Expression

3. Arrow Function

🧠 Functions are First-Class Citizens

Example:

🔁 Callback Functions

⏳ Asynchronous Functions

🚀 Promises

✨ Async/Await

🔐 Closures

🧭 Scope

🎭 The this Keyword

🏗️ Constructor Functions

🧪 Higher-Order Functions

⚙️ Behind the Scenes

🌍 Real-World Usage

🧠 Final Understanding

🧒 Simple Definition (Child Level)

🚀 Conclusion

Login Access Check

Shopping Discount System

Operators in JavaScript

Polymorphism in java

Inheritance in java

this keyword in java

OOPS (Object oriented Programming System)

Continue statement

Break statement

Jumping statement

3. Using `class` (Modern Way)

🎭 The `this` Keyword