code: function decChar(char, base = 10) {
    let val = charToVal(char);
    if (val < 0) throw new Error('in decChar, invalid character');
    val = (val + base - 1) % base;
    return consts.alphabet[val];
  }
docs: /* Decrement a character to the preceding character in consts.alphabet, modulo the given base.
  *