title: fromEvent operator with "onload" event(feat. dynamically created image element)
body: <p>I'm trying to create <code>image</code> element dynamically and undertake other work after the element is loaded like below:</p>
  
  <pre><code>const img = new Image();
  img.src = imagePath;
  
  fromEvent(img, 'onload').subscribe(() =&gt; // do something);
  </code></pre>
  
  <p>But apparently, <code>fromEvent</code> operator never emits with <code>onload</code> event. </p>
  
  <p>I saw they have discussed it in <a href="https://stackoverflow.com/questions/31366735/how-to-load-images-async-with-rxjs-and-perform-a-method-when-all-loaded">How to load images async with RxJs and perform a method when all loaded</a> but I'd like to know if there's any other workaround to achieve this without creating an observable myself like using <code>fromEvent</code>. </p>
  
  <p>Any insight would be appreciated!</p>