BehaviorSubject of a Subject

by azhwani

HTML

<div class="container">
    <div class="header">
        <div class="this"></div>
    </div>
</div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/2.3.13/rx.all.js"></script>

CSS

body {
    font-family: sans-serif;
    padding: 10px;
}
h2 {
    font-weight: bold;
    display: inline-block;
    margin-left: 20px;
}
.header {
    background: #ECECEC;
    padding: 5px;
}

JavaScript

var element = document.querySelector('.this');
var subject = new Rx.Subject();

var behavior = subject
.map(function (x) { return x*2;})
.multicast(new Rx.BehaviorSubject(null)).refCount()
.filter(function (x) { return x !== null; });

subject.onNext(6);

behavior.subscribe(function (x) {
  element.textContent = String(x);
});

// element.textContent should show '12' but shows nothing