test.ts

interface StoreOptions {

}

interface DbStoreOptions extends StoreOptions {
  dsn: string
}

interface FileStoreOptions extends DbStoreOptions {
  path: string
}

interface StoreConstructor {
  new(options: StoreOptions): IStore;
}
interface IStore {
  get(): void;
}

function createStore(ctor: StoreConstructor, options: StoreOptions): IStore {
  return new ctor(options);
}

export function factory(storeName: string, storeOptions: StoreOptions) {
  const storeMap: { [index: string]: StoreConstructor } = {
    db: DbStore,
    file: FileStore
  }
  return createStore(storeMap[storeName], storeOptions)
}


class DbStore implements IStore {
  constructor(options: DbStoreOptions) { }
  get() {
    console.log("beep beep");
  }
}
class FileStore implements IStore {
  constructor(options: FileStoreOptions) { }
  get() {
    console.log("tick tock");
  }
}


// Usage:

const store = factory('file', { path: 'test' })
store.get()