Reactive summary comparison

rsc.js

var Bacon = require('baconjs');
var Rx = require('rx');
var Kefir = require('kefir');
var EE = require('events').EventEmitter;
var ee = new EE;

var sum = function (prev, cur) {return prev+cur};

Bacon.fromEvent(ee, 'event1').scan(0, sum).onValue(console.log); // 0, 4, 9
Rx.Observable.fromEvent(ee, 'event1').reduce(sum, 0).subscribe(console.log); // doesn't work
Kefir.fromEvents(ee, 'event1').scan(sum, 0).onValue(console.log); // 0, 4, 9

ee.emit('event1', 4);
ee.emit('event1', 5);