oop-examples/typescript/inheritance/index.ts

import { Dog } from "./dog";
import { Cat } from "./cat";
import { Animal } from "./animal";

// because cat and dog are subclasses of animal, they can be stored in an array of animals
const animals: Animal[] = [
  new Dog('buster'),
  new Cat('mittens')
]

for (const a of animals) {
  // when calling the make_sound function, the implementation of the actual class gets called (in this case cat or dog)
  a.make_sound();
}