How to do the chain sequence in rxjs
<p>I would like to to something like:</p>

<pre><code>this._myService.doSomething().subscribe(result =&gt; {
  doSomething()
});
.then( () =&gt; dosthelse() )
.then( () =&gt; dosanotherthing() )
</code></pre>

<p>So I would like to chain .then like in promise. How would I do that in Rxjs?</p>

<pre><code>this._myService.getLoginScreen().subscribe( result =&gt; {
      window.location.href = MyService.LOGIN_URL;
      /// I would like to wait for the site to load and alert something from       the url, when I do it here it alerts the old one
    });
   .then (alert(anotherService.partOfTheUrl())


getLoginScreen() {
  return this.http.get(myService.LOGIN_URL)
.flatMap(result =&gt; this.changeBrowserUrl())
.subscribe( result =&gt; //i want to do sth when the page is loaded//);
}

changeBrowserUrl(): Observable&lt;any&gt; {
return Observable.create( observer =&gt; {
window.location.href = myService.LOGIN_URL;
observer.next();
});
}
</code></pre>