create-instance.ts

// When creating factories in TypeScript using generics, it is necessary to refer to class types by their constructor functions.
// For example:

function create<T>(c: { new (): T }): T {
  return new c();
}

// A more advanced example uses the prototype property to infer and constrain relationships between the constructor
// function and the instance side of class types.

class BeeKeeper {
  hasMask: boolean;
}

class ZooKeeper {
  nametag: string;
}

class Animal {
  numLegs: number;
}

class Bee extends Animal {
  keeper: BeeKeeper;
}

class Lion extends Animal {
  keeper: ZooKeeper;
}

function createInstance<A extends Animal>(c: new () => A): A {
  return new c();
}

createInstance(Lion).keeper.nametag;
createInstance(Bee).keeper.hasMask;

// https://www.typescriptlang.org/docs/handbook/generics.html#using-class-types-in-generics