Understanding Object-Oriented Programming in Javascript

Object-oriented programming is a concept of writing code in which we organize everything around objects.

An object is a combination of

1. Properties

2. Methods

Instead of writing separate variables and functions, we bundle them together.

Real-World Analogy: Blueprint → Objects

Let’s understand object-oriented programming with a simple example:

Imagine you are a car manufacturer.

You first create a blueprint (design)

• Then you use that blueprint to create multiple cars

👉 In JavaScript:

• Blueprint = Class

• Car = Object (Instance)

So instead of rewriting code again and again, we define a class once and reuse it.

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🧱 What is a Class in JavaScript?

A class is a blueprint used to create objects.

It defines:

• What properties an object will have

• What actions it can perform

Example:

class Person {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }

  greet() {
    console.log(`Hi, my name is ${this.name}`);
  }
}

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🧪 Creating Objects (Instances)

We use the new keyword to create objects from a class.

const person1 = new Person("Ashish", 25);
const person2 = new Person("Rahul", 30);

person1.greet(); // Hi, my name is Ashish
person2.greet(); // Hi, my name is Rahul

👉 Each object:

• Has its own data

• Shares the same structure and methods

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⚙️ Understanding the Constructor

The constructor is a special method inside a class.

Key Points:

• It runs automatically when an object is created

• It initializes object properties

constructor(name, age) {
  this.name = name;
  this.age = age;
}

👉 this refers to the current object.

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🔧 Methods Inside a Class

Methods define what an object can do.

greet() {
  console.log(`Hi, my name is ${this.name}`);
}

👉 Methods are shared across all instances (memory efficient).

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🔒 Basic Idea of Encapsulation

Encapsulation means:

👉 Keeping data and methods together and controlling access

Real-world example:

Think of a car:

• You don’t directly control the engine

• You use steering, brakes, accelerator

Same in code:

• Internal data is hidden

• Access is controlled via methods

Simple Example:

class BankAccount {
  constructor(balance) {
    this.balance = balance;
  }

  deposit(amount) {
    this.balance += amount;
  }

  getBalance() {
    return this.balance;
  }
}

👉 We interact using methods instead of directly modifying data.

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♻️ Why Use OOP?

OOP helps you write better code:

• ✅ Reusable (write once, use many times)

• ✅ Organized (structured code)

• ✅ Scalable (easy to expand)

• ✅ Maintainable (easy to debug and update)

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🧠 Class vs Object (Quick Comparison)

Concept	Meaning
Class	Blueprint
Object	Real instance created from class

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🎯 Assignment

Try this yourself 👇

Task:

Create a Student class with:

• Properties: name, age

• Method: printDetails()

Example Solution:

class Student {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }

  printDetails() {
    console.log(`Name: \({this.name}, Age: \){this.age}`);
  }
}

const student1 = new Student("Aman", 20);
const student2 = new Student("Neha", 22);

student1.printDetails();
student2.printDetails();

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🧩 Visual Understanding (Conceptual)

Class (Blueprint)
      ↓
Create using new
      ↓
Objects (Instances)

Example:

Car (Class)
  ↓
car1, car2, car3 (Objects)

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📌 Common Mistakes Beginners Make

❌ Forgetting new keyword ❌ Not using this properly ❌ Thinking each object has separate methods (they are shared) ❌ Confusing class with object

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🧠 Final Thoughts

OOP is not just a concept—it’s a way of thinking.

Once you understand:

• Class

• Object

• Constructor

• Methods

You can build real-world applications much more easily 🚀

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Happy Coding! 💻