"Early Return" using delimited continuations

finders.ts

// could be really expensive if the enumerable is really long.
[...worlds].find(x => x.name === "Arcadia");


// this will return early the moment that the predicate matches
function* find(enumerable, predicate) {
  return yield* shift(function*(k) {
    for (let item of enumerable) {
      if (predicate(item) {
        k(item);
        break;
      }
    }
  });
}

// now completely safe
yield* find(worlds, x => x.name === "Arcadia");