数字保留两位小数，并千分位标识 - davy-gan/web GitHub Wiki

function formatMoney(num, unit = '元') {
  if (num === '') {
    return;
  } else if (isNaN(num)) {
    return num;
  }
  return `${parseFloat(num).toFixed(2).replace(/(\d)(?=(\d{3})+\.)/g, '$1,')}${unit}`;
}

formatNum (num) {
  if (num === '') {
    return;
  } else if (isNaN(num)) {
    return num;
  }
   return (num + '').replace(/(\d{1,3})(?=(\d{3})+(?:$|\.))/g, '$1,');
}

console.log(String(12345678.321).replace(/\d{1,3}(?=(\d{3})+(\.|$))/g,'$&,'))