That's a worst case scenario and things could be worse if they hacked your production code base.
All data should be 256bit ssl encrypted for point to point security and asset tampering protection. After that, i doubt stripes js lib is much of a problem, it communicates in a secure tunnel from the client to stripe.
They as well say you don't have to worry about PCI compliance then because you are never handling financially sensitive data directly, only indirectly.