npm i int-parser --save
const parser = require('int-parser');
const base62Symbols = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
parser.parseInt(99999, base62Symbols); // => 'q0T'
const parser = require('int-paser');
const base62Symbols = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
parser.toInt('q0T', base62Symbols); // 99999