code: function encode(num) {
    var encoded = '';
  
    do {
      encoded = alphabet[num % length] + encoded;
      num = Math.floor(num / length);
    } while (num > 0);
  
    return encoded;
  }
docs: Return a string representing the specified number.
  
  @param {Number} num The number to convert.
  @returns {String} The string representation of the number.
  @api public