jquery 添加千分位

/**

• 格式化千分位
• @param strNum
• @returns
  */
  function formatNum(strNum) {
  if("-"==strNum){
  return "";
  }
  if (strNum.length <= 3) {
  return strNum;
  }
  if (!/^(+|-)?(\d+)(.\d+)?$/.test(strNum)) {
  return strNum;
  }
  var a = RegExp.$1, b = RegExp.$2, c = RegExp.$3;
  var re = new RegExp();
  re.compile("(\d)(\d{3})(,|$)");
  while (re.test(b)) {
  b = b.replace(re, "$1,$2$3");
  }
  return a + "" + b + "" + c;
  }