constructor(value) {

this._value = value;

}

static of(value) {

return new Maybe(value);

}

isNothing() {

return this._value === null || this._value === undefined;

}

map(callback) {

if (this.isNothing()) {

return Maybe.of(null);

}

return Maybe.of(callback(this._value));

}

ids.reduce(

(previousPromises, nextId) =>

previousPromises.then(() =>

fetchPokemon(nextId).then(res => console.log(res.name)),

),

Promise.resolve(),