// 无小数版本
let format = n => {let num = n.toString() let len = num.lengthif (len <= 3) {return num} else {return format(num.slice(0,len-3))+','+num.slice(len-3)}
}
let res=format(1232327666663)  // '1,232,323'
console.log(res)

// 有小数版本
let format = n => {let num = n.toString() // 转成字符串let decimals = ''// 判断是否有小数let index=num.indexOf('.') if(index>-1){decimals = num.slice(index)num=num.slice(0,index)}let len = num.lengthlet res=''if (len <= 3) {res = num} else {res = format(num.slice(0,len-3))+','+num.slice(len-3)}return decimals?res+decimals:res
}
let res=format(123232.7666663)  // '1,232,323'
console.log(res)