js实现每隔三个数加一个逗号，还要考虑小数点的情况

function transform(number){
    var num = number.toString() 
    var numArr = num.split('.')
    var [num, dotNum] = numArr


    var operateNum = num.split('').reverse()
    var result = [], len = operateNum.length
    for(var i = 0; i< len; i++){
         result.push(operateNum[i])
         if(((i+1) % 3 === 0) && (i !== len-1)){
              result.push(',')
        }
    }

    if(dotNum){
         result.reverse().push('.', ...dotNum)
         return result.join('')
    }else{
         return result.reverse().join('')
    }

}



var output=transform(1988768.89)


console.log(output)    //  1,988,768.89