JS code for formatting thousandth digits (separated by commas. The code has been modified to support commas separating 0-9 digits)_javascript skills

             if(isNumber(number) || isString(number) || REG_NUMBER.test(number)) {

                 // 先转换成字符串
                 var toString = number + '',
                     isPoint = toString.indexOf('.'),
                     prefix,   // 前缀
                     suffix,   // 后缀
                     t = '';

                 if(isPoint > 0) {
                    prefix = toString.substring(0,isPoint);
                    suffix = toString.substring(isPoint + 1);

                 }else if(isPoint == 0) {
                    prefix = '';
                    suffix = toString.substring(1);

                 }else {
                    prefix = toString;
                    suffix = '';
                 }

                 if(prefix != '') {
                    prefixArr = prefix.split('').reverse();

                    var isArrayIndex = isArray(d,numArrs);
                    if(isArrayIndex > -1) {

                        for(var i = 0, ilen = prefixArr.length; i < ilen; i =1) {
                            t = prefixArr[i] ((i 1) % isArrayIndex == 0 && (i 1) != prefixArr.length ? "," : "");
                        }
                        t = t.split("").reverse().join("");
                        if(suffix != '') {
                            return t "." suffix;
                        }else {
                            return t;
                        }

                    }else {
                        return '传入的多少位不正确';
                    }

                 }else if(prefix != '' && suffix == ''){

                    return prefix;

                 }else if(prefix == '' && suffix != ''){
                    prefix = 0;

                    return prefix suffix;
                 }else {
                     return "有错误";
                 }
            }else {
                return '传入的要格式化的数字不符合';
            }

         }
         function isArray(item,arrs) {
            for(var i = 0, ilen = arrs.length; i < ilen; i ) {
                if(item == arrs[i]) {
                    return i;
                }
            }
            return -1;
         }
         function isNumber(number) {
            return Object.prototype.toString.apply(number) === '[object Number]';
         }

         function isString(number) {
            return Object.prototype.toString.apply(number) === ['object String'];
         }