JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <div class="page-header">
        <h1>RxJS multiple subscriptions for Observable.Interval</h1>
        <ul id="list"></ul>
    </div>
</div>
<script src="//cdnjs.cloudflare.com/ajax/libs/moment.js/2.6.0/moment.min.js"></script>
<script
 src="http://cdnjs.cloudflare.com/ajax/libs/rxjs/2.1.18/rx.js"></script>
<script src="http://cdnjs.cloudflare.com/ajax/libs/rxjs/2.1.18/rx.binding.js"></script>
<script src="http://cdnjs.cloudflare.com/ajax/libs/rxjs/2.1.18/rx.time.js"></script>
<script src="http://cdnjs.cloudflare.com/ajax/libs/rxjs-dom/2.0.7/rx.dom.js"></script>

JavaScript

(function() {
    
    var list = document.getElementById("list");
    var stream = Rx.Observable.interval(1000)
    .startWith(-1)
    .select(function(){ return moment().format("D MMMM, HH:mm:ss") });
    
    stream.subscribe(function(value) {
        var li = document.createElement("li");
        
        x = 0.0;
        for (var i = 1; i < 100000000; i++)
        	x += Math.sqrt(i);
        
        li.innerHTML = "subscriber 1: "+value + " " + x;
        list.appendChild(li); 
    });    
    stream.subscribe(function(value) {
        var li = document.createElement("li");
        li.innerHTML = "subscriber 2: "+value;
        list.appendChild(li); 
    });
    
})();