数字を大文字の中国語に変換する JavaScript メソッド_JavaScript スキル

function intToChinese ( str ) {
 str = str+'';
 var len = str.length-1;
 var idxs = ['','十','百','千','万','十','百','千','亿','十','百','千','万','十','百','千','亿'];
 var num = ['零','壹','贰','叁','肆','伍','陆','柒','捌','玖'];
 return str.replace(/([1-9]|0+)/g,function( $, $1, idx, full) {
  var pos = 0;
  if( $1[0] != '0' ){
   pos = len-idx;
   if( idx == 0 && $1[0] == 1 && idxs[len-idx] == '十'){
    return idxs[len-idx];
   }
   return num[$1[0]] + idxs[len-idx];
  } else {
   var left = len - idx;
   var right = len - idx + $1.length;
   if( Math.floor(right/4) - Math.floor(left/4) > 0 ){
    pos = left - left%4;
   }
   if( pos ){
    return idxs[pos] + num[$1[0]];
   } else if( idx + $1.length >= len ){
    return '';
   }else {
    return num[$1[0]]
   }
  }
 });
}