RxJS .zip and .switchLatest

HTML

<script src="https://rawgit.com/Reactive-Extensions/RxJS/master/dist/rx.all.js"></script>

CSS

textarea {
    font-family:"Courier New", monospace;
    font-size: 12px;
    width: 100%;
    height: 120px;
}

JavaScript

var p1 = function () { return Promise.resolve(1);}
 var p2 = function (x) { return Promise.resolve(x+1); };
 var p3 = function (x) {
      var isEven = function(x) {return x % 2 === 0;};
      return Promise.resolve(isEven(x));
 };

 var chainedPromises$ = 
     Rx.Observable.just()
             .flatMap(p1)
             .flatMap(p2)
             .flatMap(p3);

chainedPromises$.subscribe(function(x){console.log(x)})