SOURCE

// 保留三位小数
console.log(parseToMoney(1234.56)) // return '1,234.56'
// console.log(parseToMoney(123456789)) // return '123,456,789'
// console.log(parseToMoney(1087654.321)) // return '1,087,654.321'
function parseToMoney(str){
    let res = ''
    str = str.toFixed(3)
    let [first, second] = str.split('.')
    // console.log(first,second)
    first = first.replace(/\d(?=(\d{3})+$)/g,'$&,')
    return [].concat(first,second).join('.')
}