title: How to track Slingshot upload progress change without using setInterval?
body: <p>I am using <a href="https://github.com/CulturalMe/meteor-slingshot" rel="nofollow">meteor-slingshot</a> to upload a file. I want to set the progress bar percentage when it changes.</p>
  
  <p>This is how I do it now.</p>
  
  <pre><code>{{percentage}}
  
  percentage: number;
  uploadButton() {
    // First start to upload
    // ...
  
    // Then track the progress
    setInterval(() =&gt; {
      this.percentage = uploader.progress();  // The API uploader.progress() returns a number
    }, 1000);
  }
  </code></pre>
  
  <p>Is there a smart way using RxJS or something else to track the number change without using <code>setInterval</code>?</p>
  
  <p>Thanks</p>