Classes

• Extends: Inherits all properties and methods from parent class

Extends

• Extends another class
• Inherits the methods from a parent class

class Car extends Vehicle {}
class NumbersCollection extends Sorter {}

Implements

• Implements a interface
• Assure that the class obeys the interface
• Check if class satisfies all the requisites in an interface

class User implements Mappable {}
class NumbersCollection implements Sortable {}

Abstract classes

• Classes that cannot be instantiated directly!
• Only used as a parent class
• Methods can refer to methods that don't exist yet
• Child classes must 'promise' to implement theses methods

abstract class Sorter {
  abstract compare(leftIndex: number, rightIndex: number): boolean;
  abstract swap(leftIndex: number, rightIndex: number): void;
  abstract length: number;
}

• Abstract keyword mark methods that will be defined in the child class

super()

• super() must be called inside of the constructor of a child class
• super() is a reference to the constructor of the parent class
• super() don't need to be called if the child does not have a constructor defined

export class CharactersCollection extends Sorter {
  constructor(public data: string) {
    super();
  }
}

Static methods

• Invoke a method without instantiating the class

class Food {
  // Static Property
  static description = 'This class represents foods!';

  // Static method
  static printDescription() {
    console.log(this.description);
  }
}