To clarify, I wouldn't bother with creating a Buffer/Uint8Array creating version right now since your underlying re-assembly logic is built using strings and this be workin' already and that's just asking to break something in the home stretch.

Also, it's also very worth noting that mailparser.js plays fast and loose with strings itself anyways, so it really would only matter when we switch to jcranmer's jsmime and hell freezes over and people start transferring stuff in 8-bit over SMTP.