Or are are there other concerns regarding JS?
Again, I would point people to this post from Greg Maxwell -
https://bitcointalk.org/index.php?topic=5324030.msg56590276#msg56590276.
Shouldn't there be a selection of RNGs available for javascript by now? Just wondering, seems a little odd to have such a massively used language without providing a secure RNG solution.
A selection of functions does nothing to address all the underlying issues outlined in the post above. The best solution is to just avoid webpage based wallet/seed/key generators.