title: How to make rxjs non ui blocking?
body: <p>I have an array of items. Each item in that array represents a row in my html table and is automatically rendered when the array of items is changing.</p>
  
  <p>I now wanted to use <code>rxjs</code> to add some items to that table when I click a button, so I did the following:</p>
  
  <pre><code>Rx.Observable.fromEvent(this.$.button, 'click')
      .switchMap(() =&gt; Rx.Observable.range(0, 10000))
      .subscribe((x) =&gt; {
          this.push('items', {id: '' + x, description: '' + x});
      });
  </code></pre>
  
  <p>But this is freezing the ui until every element is pushed into the array.
  How can I implement it so that the ui is not freezing and still responses to user inputs?</p>