Usually the first thing I check in a project like this when it ends up on HN or Reddit is their symmetric cryptography features. Not because of any particularly scientific reason, but because it's a good heuristic on whether or not it's worth the time and energy to look at the rest of the code.

Tanker's looks like this:

https://github.com/TankerHQ/sdk-js/blob/master/packages/cryp...

Seems pretty OK to me.