sampledByProperty.js

"use strict";
var Kefir = require("kefir"),
    events = require('events');

var empty = void(0);

var localEmitter = new events.EventEmitter(); //used to notify local updates to values against new or old topics
var remoteEmitter = new events.EventEmitter(); //used to notify local updates to values against new or old topics

var localProperty = Kefir.fromEvents(localEmitter, "Hello").toProperty();
var remoteProperty = Kefir.concat(Kefir.constant(empty), Kefir.fromEvents(remoteEmitter, "Hello")).toProperty();

var sampleProperty = remoteProperty.sampledBy(localProperty, function(remote, local){
    return [remote, local];
});

localProperty.log("Local");
remoteProperty.log("Remote");
sampleProperty.log("Sampled");

localEmitter.emit("Hello", "World");