Given a 32-bit signed integer, reverse digits of an integer.

Example 1:

Input: 123
Output: 321

Example 2:

Input: -123
Output: -321

Example 3:

Input: 120
Output: 21

Note:
Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231,  231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

意思就是把整数反转过来，代码如下：

var reverse = function(x) {
     var number='';
     var arr=''+x;
     var numArr=arr.split("");
     numArr.reverse();
     if(numArr[numArr.length-1]=='-'){
           number+='-';
           numArr.splice(numArr.length-1,1);
     }
     for(var i=0;i<numArr.length;i++){
           number+=parseInt(numArr[i]);
     }
         number=parseInt(number);
     if(number>Math.pow(2,31)-1||number<(-Math.pow(2,31))){
         number=0;
     }
           return number;
};