保留小数点n位且整数自动补零

/**
         * 保留小数点n位且整数自动补零
         * */ 
        pointFloor(num, n) {
            if (typeof(num) == 'number' || typeof(num) == 'string') {
                let numStr = num + "";
                let list = numStr.split('.');
                let num0 = list[0];
                let num1 = list[1] || '';
                num1 = (num1 + Array(n + 1).join(0)).slice(0, n);
                return n != 0 ? (Number(num0) + '.' + num1) : Number(num0) + '';
            } else return '';
        },