JavaScript - Size converter

/**
 * Get the human-readable size for an amount of bytes
 * @param int  size      : the number of bytes to be converted
 * @param int  precision : number of decimal places to round to;
 *                         optional - defaults to 2
 * @param bool long_name : whether or not the returned size tag should
 *                         be unabbreviated (ie "Gigabytes" or "GB");
 *                         optional - defaults to true
 * @param bool real_size : whether or not to use the real (base 1024)
 *                         or commercial (base 1000) size;
 *                         optional - defaults to true
 * @return string        : the converted size
 */
function getSize(size,precision,longName,realSize) {
   if (typeof precision=="undefined") {
      precision=2;
   }
   if (typeof longName=="undefined") {
      longName=true;
   }
   if (typeof realSize=="undefined") {
      realSize=true;
   }
   var base=realSize?1024:1000;
   var pos=0;
   while (size>base) {
      size/=base;
      pos++;
   }
   var prefix=getSizePrefix(pos);
   var sizeName=longName?prefix+"bytes":prefix.charAt(0)+'B';
   sizeName=sizeName.charAt(0).toUpperCase()+sizeName.substring(1);
   var num=Math.pow(10,precision);
   return (Math.round(size*num)/num)+' '+sizeName;
}
[javascript]
/**
 * @param int pos : the distence along the metric scale relitive to 0
 * @return string : the prefix
 */
function getSizePrefix(pos) {
   switch (pos) {
      case  0: return "";
      case  1: return "kilo";
      case  2: return "mega";
      case  3: return "giga";
      case  4: return "tera";
      case  5: return "peta";
      case  6: return "exa";
      case  7: return "zetta";
      case  8: return "yotta";
      case  9: return "xenna";
      case 10: return "w-";
      case 11: return "vendeka";
      case 12: return "u-";
      default: return "?-";
   }
}