Hm, window.trans relies on data attributes on a `div` generated by a Django block in the template. AFAIK, there's no way to get translations in JavaScript alone.

Perhaps this:

In the usage comments of this file, instruct users to include an appropriate Django block in their template (as seen here: https://github.com/mozilla/bedrock/blob/master/bedrock/firefox/templates/firefox/os/index.html#L15). 

In the implementation, if window.trans cannot find the string block mentioned above, default to English only. I'll chat with a couple people tomorrow to see if there's a better way, but I think we have to rely on the template containing the translation.