Class Inheritance in TypeScript: A Practical Example

 Introduction:

TypeScript is a powerful, typed superset of JavaScript that can help you write more organized and maintainable code. One of the key features in TypeScript is the support for class-based object-oriented programming, which includes the ability to use class inheritance. In this blog post, we will explore the basics of class inheritance in TypeScript and understand how to use it effectively in your code with a practical example.

Creating a Base Class:

To create a base class in TypeScript, you can use the class keyword. A base class defines the properties and methods that are shared among all its subclasses. For example, you can create a base class for a Shape:

class Shape {

    width: number;

    height: number;

    constructor(width: number, height: number) {

        this.width = width;

        this.height = height;

    }

    calculateArea(): number {

        return this.width * this.height;

    }

}

Creating a Subclass:

To create a subclass in TypeScript, you can use the extends keyword. A subclass inherits the properties and methods of its base class and can also define its own properties and methods. For example, you can create a subclass for a Rectangle:

class Rectangle extends Shape {

    calculateArea(): number {

        return this.width * this.height;

    }

}

Using the Subclass:

You can create an instance of a subclass and access its properties and methods, as well as those of its base class. For example, you can create a rectangle with the width and height of 2 and 4, and calculate its area:

const rectangle = new Rectangle(2, 4);

console.log(rectangle.calculateArea()); // Outputs: 8

Overriding Methods:

A subclass can override the methods of its base class by defining a method with the same name. The subclass method will be called instead of the base class method when called on an instance of the subclass. For example, you can override the calculateArea() method in the Rectangle class to return the area of a rectangle instead of the area of a shape:

class Rectangle extends Shape {

    calculateArea(): number {

        return this.width * this.height;

    }

}

Advantages of Using Class Inheritance:

• Class inheritance allows you to create a hierarchy of classes that share properties and methods.
• Class inheritance allows you to reuse code and avoid duplication.
• Class inheritance allows you to create more specialized classes that inherit the behavior of more general classes.

When to use Class Inheritance:

• When you want to create a hierarchy of classes that share properties and methods.
• When you want to reuse code and avoid duplication.
• When you want to create more specialized classes that inherit the behavior of more general classes.

Conclusion:

Class inheritance is an important feature in TypeScript that allows you to create a hierarchy of classes that share properties and methods. It allows you to reuse code and avoid duplication, as well as create more specialized classes that inherit the behavior of more general classes. Understanding how to use class inheritance in TypeScript is an essential part of developing with TypeScript, and this example provides a practical demonstration of how to use class inheritance effectively in your code.