text: export class Maybe {
  
      constructor(value) {
          this._value = value;
      }
  
      static of(value) {
          return new Maybe(value);
      }
  
      isNothing() {
          return this._value === null || this._value === undefined;
      }
  
      map(fn){
  
          if(this.isNothing()) return Maybe.of(null);
          return Maybe.of(fn(this._value))
      }
  
      getOrElse(value) {
          if (this.isNothing()) return value;
          return this._value;
      }
  }