Observable from Promise

fromPromise.js

export default function fromPromise(promise) {
  return new Observable(observer => {
    let active = true;
    promise.then((...data) => {
      if (active) {
        observer.next(...data);
      }
      observer.complete();
    }).catch((...err) => observer.error(...err));

    return () => (active = false);
  });
}