-

var Rx = require('rx');

var e1 = new Rx.Subject();
var e2 = new Rx.Subject();
var e3 = new Rx.Subject();

var e1s = e1.asObservable();
var e2s = e2.asObservable();
var e3s = e3.asObservable();

e3s.
    startWith(true).
    flatMapLatest(function () {
        return e1s.
            flatMapLatest(function () {
                return e2s.delay(1000);
            }).
            takeUntil(e3s);
    }).
    forEach(function (value) {
        console.log('value %s', value);
    });

// NOT emit e2
e1.onNext('e1');
e2.onNext('e2');
setTimeout(function () {
    // abort e2
    e3.onNext('e3');
}, 500);

setTimeout(function () {
    e1.onNext('e1');
    // should emit e2 since e3 is not happened
    e2.onNext('e2');
}, 2000);