enum.ts

interface IEnum<T = void> {
  key: string;
  value: T;
}
interface IEnumConstructor<T = void> {
  new(value: T): IEnum<T>;
  enumKeys: Set<string>;
  enumValues: Set<IEnum<T>>;
}

class EnumClass<T = void> {
  protected static readonly _enumList: Array<EnumClass> = [];

  private static _enumValues: Set<EnumClass>;
  public static get enumValues(): Set<EnumClass> {
    return this._enumValues || (this._enumValues = new Set(this._enumList.filter((item) => item.key)));
  }

  private static _enumKeys: Set<string>;
  public static get enumKeys(): Set<string> {
    return this._enumKeys || (this._enumKeys = new Set(this._enumList.map((item) => item.key).filter(Boolean)));
  }

  private _key?: string;
  public get key(): string {
    return this._key || (this._key = (Object.keys(this.constructor).find((itemKey: string) => (this.constructor as any)[itemKey] === this) as string));
  }

  constructor(public value: T) {
    (this.constructor as typeof EnumClass)._enumList.push(this as unknown as EnumClass);
  }

  public toString(): string {
    return `${this.constructor.name}.${this.key}`;
  }
}

function Enum<T = void>() {
  return class EnumClassItem extends EnumClass<T> {
    protected static readonly _enumList: Array<EnumClass> = [];
  } as unknown as IEnumConstructor<T>;
}

// Example:

// Define the enum
class YesNo extends Enum<number>() {
  static Yes = new YesNo(1);
  static No = new YesNo(2);
}

// Works with multiple enums
class YesNoMaybe extends Enum<string>() {
  static Yes = new YesNoMaybe('Yeah');
  static No = new YesNoMaybe('Nah');
  static Maybe = new YesNoMaybe('Meh');
}

// Can be done, but won't influence the enum
const maybe = new YesNo(3);
const iDontKnow = new YesNo(4);
const canYouRepeatTheQuestion = new YesNo(5);

// Expected results
console.log(String(YesNo.Yes)); // 'YesNo.Yes'
console.log(YesNo.enumKeys.has('Yes')); // true
console.log(YesNo.enumKeys.has('Maybe')); // false
console.log(YesNo.enumKeys.has('Yesss!')); // false
console.log(YesNo.enumKeys.size); // 2
console.log(YesNo.enumValues.size); // 2
console.log(YesNo.Yes.key); // Yes
console.log(YesNo.Yes.value); // 1
console.log(YesNoMaybe.enumKeys.size); // 3