I guess `emitter.js` was a bad example because it doesn't use `@return`. Mind adding it in? Example https://github.com/mozilla-b2g/gaia/blob/8b478f6ed565075e3c0e1f5400743ba4e75950bc/apps/sms/js/compose.js#L461-L464

Also here and below: write "opts" as "[opts]" [to signal that it is optional](http://usejsdoc.org/tags-param.html)