var reverse = function(x) {
   let borderValue = Math.pow(2, 31);
   let reverseStr = x.toString().split('').reverse().join('');
   let value;
   if (x < 0) { // 为负数
       value = Number('-' + reverseStr.slice(0, -1));
       return value > -borderValue ? value : 0;
   } else { 
       value = Number(reverseStr);
       return value < borderValue -1 ? value : 0;
   }
};