128-bit integers do not serialize accurately in javascript
While developing my wave file ksy, I found that generated JavaScript code does not accurately serialize 8-byte integers, i.e. u8's.  Precision is lost in the low bits of the u8 when a WAV file is parsed. 

I noticed this specifically when parsing a GuidType in my wav.ksy, which under normal circumstances would contain a u8.

I am supposing that JavaScript stores these values as floats or some other reduced precision format and then moves them back to integer format, thus losing low bits of precision.

All formats should be sanity checked to make sure they handle u8's with sufficient bits of precision.  If a format contains a u8, it really ought to have test data proving that u8's can be serialized correctly on all platforms.

A sort-of-workaround for ksy authors is to use a pair of u4's to insure that all bits are serialized.