const promiseResolve = () => {

  return new Promise(resolve => setTimeout(() => resolve('resolve!!'), 3000));

};

​

Rx.Observable.from(promiseResolve()).subscribe(

  x => console.log(`next: ${x}`),

  error => console.error(`error: ${error}`),

  () => console.log('complete')

);

// 3秒後に以下がコンソール出力される

// => "next: resolve!!"

// => "complete"

​

const promiseReject = () => {

  return new Promise((resolve, reject) => setTimeout(() => reject('reject!!'), 3000));

};

​

Rx.Observable.from(promiseReject()).subscribe(

  x => console.log(`next: ${x}`),

  error => console.error(`error: ${error}`),

  () => console.log('complete')

);

// 3秒後に以下がコンソール出力される

// => error: reject!!