实现千位分隔符

console.log(parseToMoney(1234.56))
console.log(parseToMoney(12345678))
console.log(parseToMoney(1087654.321))

function parseToMoney(num) {
  num = parseFloat(num.toFixed(3));
  let [integer, decimal] = String.prototype.split.call(num, '.');
  integer = integer.replace(/\d(?=(\d{3})+$)/g, '$&,');
  return integer + (decimal ? '.' +decimal : '');
}