var obs1 = Rx.Observable.throw(new Error('error'));

var obs2 = Rx.Observable.return(42);

​

var source = Rx.Observable.catch(obs1, obs2);

​

var subscription = source.subscribe(

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

  e => console.log(`onError: ${e}`),

  () => console.log('onCompleted'));

​

// => onNext: 42

// => onCompleted