题解 | #乘法#

    function multiply(a, b) {
        let len1 = a.toString().indexOf('.') == -1 ? 0 : a.toString().split('.')[1].length;
        let len2 = b.toString().indexOf('.') == -1 ? 0 : b.toString().split('.')[1].length;
        let len = len1 < len2 ? len2 : len1;
        return (a * b).toFixed(len);
    }