Hello! Today's journey ventures into the cornerstone of TypeScript's object-oriented fundamentals: Encapsulation. This concept establishes a protective barrier around an object's data, thereby preventing it from being accessed by the external code ecosystem. Let's dive in.

Encapsulation serves three main purposes: it maintains integrity, controls data modification, and provides data abstraction — interfaces that are accessible to users. Think of using a cell phone; you interact with an interface without interfering with its circuits. Following this logic, encapsulation safeguards the internal implementation while exposing safe interfaces.

Now, let's discuss Private Data: In TypeScript, we can specify private data using the keyword private. These data fields cannot be accessed outside the class. We will illustrate this with a Car class, introducing a private attribute called _speed:

class Car {
    private _speed: number; // private speed attribute

    constructor() {
        this._speed = 0; // Initialize speed with 0
    }
}

This class has a private member, _speed, which cannot be accessed directly outside the class. The underscore _ before speed is a naming convention that indicates it is a private attribute.

Getters and Setters are tools used to control access to private data. In our Car class, a getter function retrieves the _speed attribute, while a setter function modifies it as follows:

class Car {
    private _speed: number; // Private speed attribute

    constructor() {
        this._speed = 0; // Initialize speed with 0
    }

    get speed(): number { // Get current speed
        return this._speed;
    }

    set speed(value: number) { // Update speed
        // Speed should stay in the range 0 to 150
        if (value < 0) {
            this._speed = 0;
        } else if (value > 150) {
            this._speed = 150;
        } else {
            this._speed = value;
        }
    }
}

These methods allow us to retrieve or change the car's speed in a safe manner.