[leetcode]7 反转整数

Reverse digits of an integer.

Example1: x = 123, return 321
Example2: x = -123, return -321

 function div(a, b) { //去掉小数点的除法
            return ~~(a / b)
        }
        function reverseInteger(num) {
            var ret = 0;
            var factor = num < 0 ? - 1 : 1;
            num = num * factor //变成正数
            while (num !== 0) {
                ret = ret * 10 + num % 10;
                num = div(num, 10) //不断取前几位
            }
            if ((ret > Math.pow(2, 31) - 1)) {
                return 0;
            }
            return ret * factor
        }
        reverseInteger(123)
        reverseInteger(2060)