I’d prefer to use the `hidden` property rather than the attribute (please check that it still works):
```javascript
    if (isEmpty) {
      downloadsContainer.hidden = true;
      emptyDownloadsContainer.hidden = false;
    } else {
      downloadsContainer.hidden = false;
      emptyDownloadsContainer.hidden = true;
    }
```

If we have to use the `hidden` attribute, to turn it on its value should either an empty string or `"hidden"`, not `true`:
```javascript
downloadsContainer.setAttribute('hidden', 'hidden'); // preferred
// downloadsContainer.setAttribute('hidden', ''); <-- works but misleading
emptyDownloadsContainer.removeAttribute('hidden');
```
http://www.w3.org/html/wg/drafts/html/master/infrastructure.html#boolean-attributes-0

I mention this because I think it makes the code clearer, and it avoids mistakes such as `downloadsContainer.setAttribute('hidden', false);` which wouldn’t work. Yes, I already saw that in a patch, and from one of our most brilliant developers. :)