js 保留两位小数

<script>
        var n = 19.7532424
        console.log(floatNum(n,2))

        function floatNum(num, n) {
            if(typeof num === 'number'){
                num = num.toString()
                if(num.lastIndexOf('5') != -1){
                    num = num+'1'  
                }
            }
            var f = parseFloat(num);
            if (isNaN(f)) {return false}
            f = Math.round(num * Math.pow(10, n)) / Math.pow(10, n); 
            var s = f.toString();

            var rs = s.indexOf('.');
            //判定如果是整数，增加小数点再补0
            if (rs < 0) {
                rs = s.length;
                s += '.';
            }
            while (s.length <= rs + n) {
                s += '0';
            }
            return s;
        }

    </script>