nurl/base58.js

// var alphabet = "123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ";
const alphabet = 'bMJZSrnxEyq8kN3UYQL5oXwV7BCFRtvpmDf1shAuHzKicTjeG29Pg4adW6';

const base = alphabet.length;

function encode(num) {
  let encoded = '';
  while (num) {
    const remainder = num % base;
    num = Math.floor(num / base);
    encoded = alphabet[remainder].toString() + encoded;
  }
  return encoded;
}

function decode(str) {
  let decoded = 0;
  while (str) {
    const index = alphabet.indexOf(str[0]);
    const power = str.length - 1;
    decoded += index * (Math.pow(base, power));
    str = str.substring(1);
  }
  return decoded;
}

module.exports.encode = encode;
module.exports.decode = decode;