phpjs/functions/math/hexdec.js

php.js offers community built php functions in javascript

function hexdec(hex_string) {
  //  discuss at: http://phpjs.org/functions/hexdec/
  // original by: Philippe Baumann
  //   example 1: hexdec('that');
  //   returns 1: 10
  //   example 2: hexdec('a0');
  //   returns 2: 160

  hex_string = (hex_string + '')
    .replace(/[^a-f0-9]/gi, '');
  return parseInt(hex_string, 16);
}