I just noticed this check didn't exclude Android for Firefox. And I'm not sure the check for `navigator.platform` is needed.

* Android for Firefox: `Mozilla/5.0 (Android; Mobile; rv:26.0) Gecko/26.0 Firefox/26.0`
* Firefox OS: `Mozilla/5.0 (Mobile; rv:26.0) Gecko/26.0 Firefox/26.0`

Is this enough? `if (/Firefox/.test(ua) && /Mobile|Tablet/.test(ua) && !(/Android/.test(ua)))`