isHex

assert( isHex("00"c) );
assert( isHex("FF"c) );
assert( isHex("Ffae0"c) );
assert( isHex("AB"c) );
assert( isHex("abdef"c) );
assert( isHex("ABCD"c) );
assert( isHex("0A12CD00"c) );
assert( isHex("FFFFFFFFFFFFFFFF"c) );

assert( isHex("00ER"c) == false );
assert( !isHex("0xW"c) );