var source = Rx.Observable

    .fromArray([

        Rx.Notification.createOnNext(42),

        Rx.Notification.createOnError(new Error('woops'))

    ])

    .dematerialize();

​

var subscription = source.subscribe(

    function (x) {

        console.log('Next: ' + x.toString());

    },

    function (err) {

        console.log('Error: ' + err);   

    },

    function () {

        console.log('Completed');   

    });

​

// => Next: 42

// => Error: Error: woops