Design Patterns

Strategy pattern

https://en.wikipedia.org/wiki/Strategy_pattern

State pattern

https://en.wikipedia.org/wiki/State_pattern

Null object pattern

https://en.wikipedia.org/wiki/Null_object_pattern

class Dog {
  sound() {
    return 'bark';
  }
}

class NullAnimal {
  sound() {
    return null;
  }
}

function getAnimal(type) {
  return type === 'dog' ? new Dog() : new NullAnimal();
}

['dog', null].map((animal) => getAnimal(animal).sound());
// Returns ["bark", null]