Introduction to Object-Oriented Programming (OOP) in JavaScript

As programs grow larger, organizing code becomes more important. Object-Oriented Programming (OOP) is a programming approach that helps structure code using objects and classes.

OOP focuses on modeling real-world entities in code and encourages reusability, organization, and clarity.

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What is Object-Oriented Programming?

Object-Oriented Programming (OOP) is a programming style where we organize code around objects rather than just functions and variables.

An object represents something in the real world and contains:

• Properties → data about the object
• Methods → actions the object can perform

Example:

A person may have:

• name
• age
• city

And actions like:

• introduce themselves
• walk
• speak

OOP allows us to represent these structures in code.

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Real-World Analogy: Blueprint → Objects

A good way to understand OOP is through a blueprint analogy.

Imagine a car factory.

• A blueprint defines how a car should be built.
• Many cars can be created from the same blueprint.

In programming:

Real World	Programming
Blueprint	Class
Car	Object

A class defines the structure, and objects are created from that structure.

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What is a Class in JavaScript?

A class is a template used to create objects.

It defines:

• what properties objects will have
• what methods objects can use

Example:

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

Here:

• Person is the class
• name and age are properties

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Creating Objects Using Classes

Objects are created from classes using the new keyword.

Example:

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

let person1 = new Person("Alice", 25);
let person2 = new Person("Bob", 30);

console.log(person1.name);
console.log(person2.age);

Output:

Alice
30

Each object gets its own data.

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Constructor Method

The constructor is a special method used when creating objects from a class.

It is used to initialize properties.

Example:

class Car {
  constructor(brand, model) {
    this.brand = brand;
    this.model = model;
  }
}

let car1 = new Car("Toyota", "Corolla");

console.log(car1.brand);

Output:

Toyota

The constructor runs automatically when a new object is created.

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Methods Inside a Class

Classes can also contain methods, which define actions for objects.

Example:

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

  greet() {
    console.log("Hello, my name is " + this.name);
  }
}

let person1 = new Person("Alice", 25);

person1.greet();

Output:

Hello, my name is Alice

Here:

• greet() is a method
• this.name refers to the object's name

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Basic Idea of Encapsulation

Encapsulation means keeping data and related behavior together inside an object.

Instead of spreading data and functions across the program, OOP groups them inside classes.

Example:

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

  introduce() {
    console.log("I am " + this.name + " and I am " + this.age + " years old.");
  }
}

Here:

• The data (name, age)
• And the behavior (introduce())

are kept together inside the class.

This makes code easier to understand and maintain.

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Why Use OOP?

Object-Oriented Programming helps developers:

• Organize large programs
• Reuse code efficiently
• Model real-world systems
• Keep code cleaner and easier to maintain

Many modern applications rely heavily on OOP concepts.

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Assignment

Questions

1. Create a class called Student.

2. Add properties such as:

• name
• age

1. Add a method that prints the student details.

2. Create multiple student objects using the class.

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Answers

1. Create the Student Class

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

  printDetails() {
    console.log("Student Name: " + this.name);
    console.log("Age: " + this.age);
  }
}

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2. Create Student Objects

let student1 = new Student("Rahul", 20);
let student2 = new Student("Anita", 22);

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3. Call the Method

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

Output:

Student Name: Rahul
Age: 20

Student Name: Anita
Age: 22

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Conclusion

Object-Oriented Programming helps structure code using classes and objects. A class acts as a blueprint, and objects are created from that blueprint.

By using constructors and methods, we can represent real-world entities clearly in code. Learning OOP is an important step toward writing organized, reusable, and scalable JavaScript programs.