phpjs/functions/math/base_convert.js

php.js offers community built php functions in javascript

function base_convert(number, frombase, tobase) {
  //  discuss at: http://phpjs.org/functions/base_convert/
  // original by: Philippe Baumann
  // improved by: Rafał Kukawski (http://blog.kukawski.pl)
  //   example 1: base_convert('A37334', 16, 2);
  //   returns 1: '101000110111001100110100'

  return parseInt(number + '', frombase | 0)
    .toString(tobase | 0);
}