title: Lazy loading ngFor
body: <p>I have a problem with the lazy loading and Angular4. I have a a ngFor like this:</p>
  
  <pre><code>&lt;div *ngFor="let wid of widgets"&gt;&lt;/div&gt;`
  </code></pre>
  
  <p>the wid is like:</p>
  
  <pre><code>&lt;div&gt;
   &lt;iframe [src]="url"&gt;&lt;/iframe&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>and I need the wid start to load the iframe only when visible on the screen. Does somebody knoow any trick or module for Angular2/4? Unfortunately I cannot use jQuery.</p>