Is it possible to add Teardown logic to an already existing Observable?
<p>For instance, I'm currently calling <code>unsubscribe</code> from an <code>Observable</code> that is returned from Angular 2's HTTP module.</p>
<p>But I need to have some custom logic surrounding it.</p>
<p>Is it possible to add custom teardown logic to an already existing <code>Observable</code>, like the one returned from Angular 2's HTTP module?</p>
<p>Something along the lines of:</p>
<pre class="lang-js prettyprint-override"><code>Observable.prototype.whenUnsubscribed(customTeardownLogic)
</code></pre>