One more thing that I just realized is that this is quite inefficient in most cases, since in normal circumstances every part of this statement would need to be checked (given that PDF.js uses `auto`, `page-actual`, `page-fit` and `page-width` as predefined zoom values).
Since we already guard against undefined zoom values in `page_view.js` (https://github.com/mozilla/pdf.js/blob/master/web/page_view.js#L377), wouldn't it be simpler to just replace all of this with:
```
} else if (zoomArg.indexOf('Fit') === 0) {
```

@yurydelendik Would this simplification be OK?