Return to Answer

class Cat {
  constructor(options = {}) {
    this.name = options.name ?? '';
    this.age = options.age ?? 0;
  }
  toString() {
    return `[Cat name="${this.name}", age="${this.age}"]`
  }
  toJSON() {
    const { age, name } = this;
    return { name, age };
  }
  static fromObject(obj) {
    const { name, age } = obj ?? {};
    return new Cat({ name, age });
  }
}

const cats = [
  Cat.fromObject({ name: 'Furball', age: 2 }),
  Cat.fromObject({ name: 'Artemis', age: 5 })
];

console.log(cats.toString());
console.log(JSON.stringify(cats, null, 2));

.as-console-wrapper { top: 0; max-height: 100% !important; }

class Cat {
  constructor(options = {}) {
    this.name = options.name ?? '';
    this.age = options.age ?? 0;
  }
  toString() {
    return `[Cat name="${this.name}", age="${this.age}"]`
  }
  toJSON() {
    return { name: this.name, age: this.age };
  }
  static fromObject(obj) {
    const { name, age } = obj ?? {};
    return new Cat({ name, age });
  }
}

/*
 * JSON Set adds the missing methods:
 * - toJSON
 * - toString
 */
class JSONSet extends Set {
  constructor(values) {
    super(values)
  }
  toString() {
    return super
      .toString()
      .replace(']', ` ${[...this].map(v => v.toString())
      .join(', ')}]`);
  }
  toJSON() {
    return [...this];
  }
}

const cats = new JSONSet([
  Cat.fromObject({ name: 'Furball', age: 2 }),
  Cat.fromObject({ name: 'Artemis', age: 5 })
]);

console.log(cats.toString());
console.log(JSON.stringify(cats, null, 2));

.as-console-wrapper { top: 0; max-height: 100% !important; }

class Cat {
  constructor(options = {}) {
    this.name = options.name ?? '';
    this.age = options.age ?? 0;
  }
  toString() {
    return `[Cat name="${this.name}", age="${this.age}"]`
  }
  toJSON() {
    const { age, name } = this;
    return { name, age };
  }
  static fromObject(obj) {
    const { name, age } = obj ?? {};
    return new Cat({ name, age });
  }
}

const cats = [
  Cat.fromObject({ name: 'Furball', age: 2 }),
  Cat.fromObject({ name: 'Artemis', age: 5 })
];

console.log(cats.toString());
console.log(JSON.stringify(cats, null, 2));

.as-console-wrapper { top: 0; max-height: 100% !important; }