Encapsulation

Encapsulation is a fundamental principle in object-oriented programming (OOP) that involves bundling the data (attributes) and methods (functions) that operate on the data into a single unit called a class. It restricts direct access to some of the object’s components, which can prevent the accidental modification of data.

Encapsulation helps to hide the internal state and implementation details of an object from the outside world, exposing only what is necessary through a public interface (methods). This is often achieved using access modifiers (such as private, protected, and public) to control the visibility of class members.

Key Concepts of Encapsulation:

1. Classes and Objects: Encapsulation is implemented through classes, which define the structure and behavior of objects. Objects are instances of classes.
2. Access Modifiers: These control the visibility of class members:
   • Private: Members are accessible only within the same class.
   • Protected: Members are accessible within the same class and its subclasses.
   • Public: Members are accessible from any other code.
3. Getter and Setter Methods: These methods provide controlled access to private attributes. Getters return the value of an attribute, while setters modify the value of an attribute.

Example: Consider a class representing a bank account with encapsulated data:

class BankAccount {
    constructor(owner, balance) {
        this._owner = owner; // Private attribute (conventionally indicated by an underscore)
        this._balance = balance; // Private attribute
    }

    // Getter for balance
    getBalance() {
        return this._balance;
    }

    // Setter for balance with validation
    deposit(amount) {
        if (amount > 0) {
            this._balance += amount;
        }
    }

    // Method to withdraw money with validation
    withdraw(amount) {
        if (amount > 0 && amount <= this._balance) {
            this._balance -= amount;
        }
    }
}

// Creating an instance of BankAccount
const myAccount = new BankAccount('Alice', 1000);
console.log(myAccount.getBalance()); // Output: 1000
myAccount.deposit(500);
console.log(myAccount.getBalance()); // Output: 1500
myAccount.withdraw(200);
console.log(myAccount.getBalance()); // Output: 1300