JavaScript mutual conversion between decimal and 62

function string10to62(number) {  var chars = '0123456789abcdefghigklmnopqrstuvwxyzABCDEFGHIGKLMNOPQRSTUVWXYZ'.split(''),    radix = chars.length,    qutient = +number,    arr = [];  do {    mod = qutient % radix;    qutient = (qutient - mod) / radix;    arr.unshift(chars[mod]);  } while (qutient);  return arr.join('');}function string62to10(number_code) {  var chars = '0123456789abcdefghigklmnopqrstuvwxyzABCDEFGHIGKLMNOPQRSTUVWXYZ',    radix = chars.length,    number_code = String(number_code),    len = number_code.length,    i = 0,    origin_number = 0;  while (i < len) {    origin_number += Math.pow(radix, i++) * chars.indexOf(number_code.charAt(len - i) || 0);  }  return origin_number;}