TypeScript で Cloneメソッドを実装する(浅いコピー)

TypeScriptでCloneメソッドを実装しようとしたら、手こずってしまったので備忘録で書き残しておきます

// Shallow clone example

interface Constructor<M> {
  new (...args: unknown[]): M;
}

class Bear {
  /** born on */
  public readonly bornOn: Date;

  constructor(params: { bornOn: Date }) {
    this.bornOn = params.bornOn;
  }

  public clone() {
    const constructor = this.constructor as Constructor<this>;
    return new constructor(this);
  }
}

class PetBear extends Bear {
  /** name */
  public readonly name: string;

  constructor(params: { bornOn: Date; name: string }) {
    super(params);
    this.name = params.name;
  }
}

const bear = new Bear({ bornOn: new Date("1858-10-27") });
const pooh = new PetBear({
  bornOn: new Date("1921-08-21"),
  name: "Red shirt Pooh",
});
const clonedBear = bear.clone(); // const clonedBear: Bear
const clonedPooh = pooh.clone(); // const clonedPooh: PetBear

console.log(clonedBear);
console.log(clonedPooh);