Number.prototype.toLocaleString()

(999999999).toLocaleString(); // 999,999,999
// 还可以加参数，进行更优雅的做法
const options = {
  style: 'currency',//  style: 'currency'注释掉就没有 ￥ 符号
  currency: 'CNY',
};
(999999).toLocaleString('zh-CN', options); // ¥999,999.00

js实现

export const moneyFormat = (number, decimals, dec_point, thousands_sep) => {
  number = (number + '').replace(/[^0-9+-Ee.]/g, '')
  const n = !isFinite(+number) ? 0 : +number
  const prec = !isFinite(+decimals) ? 2 : Math.abs(decimals)
  const sep = typeof thousands_sep === 'undefined' ? ',' : thousands_sep
  const dec = typeof dec_point === 'undefined' ? '.' : dec_point
  let s = ''
  const toFixedFix = function(n, prec) {
    const k = Math.pow(10, prec)
    return '' + Math.ceil(n * k) / k
  }
  s = (prec ? toFixedFix(n, prec) : '' + Math.round(n)).split('.')
  const re = /(-?\d+)(\d{3})/
  while (re.test(s[0])) {
    s[0] = s[0].replace(re, '$1' + sep + '$2')
  }
  if ((s[1] || '').length < prec) {
    s[1] = s[1] || ''
    s[1] += new Array(prec - s[1].length + 1).join('0')
  }
  return s.join(dec)
}
moneyFormat(10000000) // 10,000,000.00
moneyFormat(10000000, 3, '.', '-') // 10-000-000.000