Inheritance in Typescript

Inheritance in TypeScript allows you to create a new class based on an existing class. This is useful for creating a hierarchy of classes that share common characteristics while allowing for specific variations. TypeScript uses the extends keyword to establish inheritance.

Here’s an overview of how inheritance works in TypeScript, along with some examples:

Basic Inheritance

You define a base class and a derived class that extends the base class:

class Animal {
  name: string;

  constructor(name: string) {
    this.name = name;
  }

  move(distance: number = 0) {
    console.log(`${this.name} moved ${distance} meters.`);
  }
}

class Dog extends Animal {
  bark() {
    console.log('Woof! Woof!');
  }
}

const dog = new Dog('Tiger');
dog.bark();  // Output: Woof! Woof!
dog.move(10);  // Output: Rex moved 10 meters.

In this example:

• Animal is the base class.
• Dog is the derived class that extends Animal.
• The Dog class inherits the name property and the move method from the Animal class.

Overriding Methods

A derived class can override methods from the base class:

class Bird extends Animal {
  move(distance: number = 0) {
    console.log(`${this.name} flew ${distance} meters.`);
  }
}

const bird = new Bird('crow');
bird.move(10);  // Output: crow flew 10 meters.

Here, the move method in the Bird class overrides the move method in the Animal class.

Using super

You can call methods from the base class using the super keyword:

class Snake extends Animal {
  constructor(name: string) {
    super(name);  // Call the base class constructor
  }

  move(distance: number = 5) {
    console.log('Slithering...');
    super.move(distance);  // Call the base class method
  }
}

const snake = new Snake('Slither');
snake.move();  // Output: Slithering... Slither moved 5 meters.

In this example:

• The Snake class calls the constructor of the Animal class using super(name).
• The move method in the Snake class calls the move method of the Animal class using super.move(distance).