BehaviorSubject of a Subject

HTML

<div class="container">
    <div class="header">
        <div class="this"></div>
    </div>
</div>
<script src="http://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.shareReplay(1);

var k=behavior.subscribe(function (x) {alert(x)}); 


setTimeout(function (){subject.onNext(new Date());
},2000)
 
 k.unsubscribe();



setTimeout(function (){behavior.subscribe(function (x) {alert(x)});
},3000) 

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

*/
// element.textContent shows '12', which is correct