string to hex string /hex string to string conversion

String append with += is definitely pretty efficient - as the string will be appended rather than copied to a new string each time.

That's a great use of String.fromCharCode.apply in fromByteArray - however there is actually E.toString which allows you to do that in one big chunk (because there didn't seem to be a nice way in JS itself).

@Kartman yes, the code is a bit cryptic! Unfortunately there's nothing built-in. Node.js has Buffer.toString(encoding) which would have been perfect, but we don't have Buffer in Espruino - just DataView which is depressingly similar, but without a .toString(encoding) option