npm install bigint-base-converter
var convertBase = require('bigint-base-converter');
convertBase(value, fromBase, toBase)
toBase may be integers or alphabet strings. If integer, the output/intput will (be/expected to be) an array of numbers in that base. If string, the output/input will (be/expected to be) encoded using the characters in the string as the digits (with the base as the length of the string parameter).